Ergonomic and adjustable respiratory mask assembly with cushion

ABSTRACT

A respiratory mask assembly for delivering breathable gas to a patient includes a frame having a front surface and a rear surface adapted in use to face the patient. A cushion having a side wall is removably attachable to the frame. The cushion has a rim extending away from the side wall, and a membrane provided to substantially surround the rim. An inner edge of the membrane defines an aperture, the aperture having a generally trapezoidal shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. ProvisionalApplications of Moore et al., Ser. Nos. 60/377,254, 60/397,195, and60/402,509, the entireties of which are hereby incorporated into thepresent application by reference.

FIELD OF THE INVENTION

[0002] The invention relates to a nasal mask for use in the delivery ofNon-invasive Positive Pressure Ventilation (NPPV) and for nasalcontinuous positive airway pressure (nasal CPAP) therapy of sleepdisordered breathing (SDB) conditions such as obstructive sleep apnea(OSA).

BACKGROUND OF THE INVENTION

[0003] The application of nCPAP for treatment of OSA was taught bySullivan in U.S. Pat. No. 4,944,310, incorporated herein by reference inits entirety. In nCPAP treatment of OSA, pressurized air or otherbreathable gas is provided to the entrance of a patient's airways at apressure elevated above atmospheric pressure, typically in the range 4to 20 cm H₂O to “splint” open the patient's upper airways and preventapneas.

[0004] Apparatus to deliver nasal CPAP and NPPV therapy typicallycomprises a blower, an air delivery conduit and a patient interface. Theblower may be programmed to deliver a range of different forms oftherapy. In one form, a constant pressure of air or breathable gas isprovided to the patient. It is also known for the level of treatmentpressure to vary from breath to breath in accordance with patient need,that form of treatment being known as automatically adjusting nasal CPAPtreatment as described in U.S. Pat. No. 5,245,995 (Sullivan and Lynch),incorporated herein by reference in its entirety. NPPV is another formof treatment for breathing disorders. In its most basic form, arelatively higher pressure of gas may be provided in the patient maskduring the inspiratory phase of respiration and a relatively lowerpressure or atmospheric pressure being provided in the patient maskduring the expiratory phase of respiration. In other modes, the pressurecan be made to vary in a complex manner throughout the respiratorycycle. For example, the pressure at the mask during inspiration orexpiration can be varied through the period of treatment. See, forexample, U.S. Pat. No. 5,704,345 and International Patent PublicationNos. WO98/12965 and WO99/61088, all of which are incorporated byreference herein in their entireties. In this specification, the termNPPV therapy will be used to describe all these forms of NPPV and nasalCPAP therapy.

[0005] The patient interface for NPPV therapy may take many forms, suchas a nasal mask assembly, a nose and mouth mask assembly, nasal cushionsor a nasal prongs or pillows assembly. A mask assembly typicallyincludes a rigid shell, a soft face-contacting cushion, a foreheadsupport and headgear for securing the mask to the head.

[0006] In one known mask assembly, the headgear includes a cap portionwith four straps. In use, the cap portion engages the occipital portionof the patient. Furthermore, in use, the two lower straps extend betweenthe cap portion and a nasal mask while the two upper straps extendbetween the cap portion and a forehead support. See, for example, U.S.Pat. No. 6,119,693 (Kwok, Matchett and Grant), incorporated herein byreference in its entirety.

[0007] Some patient interfaces include quick or convenient releasemechanisms for enabling a patient and/or clinician to disengage from theblower, blower tube and/or the mask/headgear assembly. Quick orconvenient release mechanisms are useful where NPPV therapy needs to betemporarily interrupted or where a system failure causes a cessation ofgas flow to the patient interface. For example, as disclosed in U.S.patent application Ser. No. 09/482,718, incorporated herein by referencein its entirety, the headgear and mask can be removed from the patientby pulling a conveniently located cord to decouple hook and loopfasteners between engaging headstraps that are positioned, for example,at the rear of the headgear assembly. In another example, as disclosedin U.S. patent application Ser. No. 09/504,220, incorporated herein byreference in its entirety, the headgear/mask assembly can be removedfrom the patient by detaching a connector member for the headstrap,which connector member is connected directly to the frame of the mask.See also U.S. Pat. No. 3,990,727, which discloses a quick detachablecoupler that appears to be employed by the SleepNet™ IQ™ mask.

[0008] Since the patient must be able to sleep while wearing the patientinterface, it is desirable that it be comfortable. In addition, thepatient interface should provide a good seal to prevent or reduce leaks,or to better control any leak that occurs and to maintain efficacy oftreatment. Since the shape of people's noses, faces and heads varywidely, from a commercial perspective, it is important to be able tomanufacture patient interfaces which can accommodate this range offacial shapes without having to carry excessive inventory through alarge number of sizes. A number of patient interfaces have been designedwith the goals of patient comfort, ease of use, adjustability and theability to accommodate a wide range of patient face and head shapes inmind.

[0009] U.S. Pat. No. 5,243,971 (Sullivan and Bruderer) provides apatient interface (both nasal and full-face masks) that is suitable foruse in NPPV therapy. The mask has a face contacting portion mounted to ashell which is sized and shaped to overfit the nose region of anintended wearer, and the face contacting portion is in the form of adistendable membrane which is molded from an elastic material. U.S. Pat.No. 5,243,971 is hereby incorporated by reference in its entirety.

[0010] U.S. Pat. Nos. 6,357,441 and 6,112,746 (Kwok and Styles) eachdescribe a nasal cushion which comprises a substantially triangularlyshaped frame from which extends a membrane. These patents are herebyincorporated by reference in their entirety.

[0011] Other nasal masks are disclosed in U.S. Pat. Nos. 5,724,965 and6,119,694, incorporated by reference in their entirety. Each describes anasal cushion that engages with the tip of the nose or that portion ofthe nose in the horizontal plane just above the upper lip of thepatient. In PCT/US00/11329 (WO 00/69521), incorporated by reference inits entirety, a triangular-shaped nasal cushion includes a taperedprofile that narrows towards the face of the patient. Some of theseprior art masks/cushions has experienced significant challenges from theperspective of patient comfort, potential nasal vent occlusion,stability and/or sealing (especially at the nasal bridge and cheekregions).

[0012] A number of adjustable forehead supports have been developed withthe aim of achieving a serviceable seal while increasing patient comfortand accommodating the greatest number of patients in the population. Forexample, U.S. Pat. No. 6,119,693 (Kwok, Matchett and Grant) describes anadjustable forehead support for a nasal mask or full-face mask. Theforehead support may be adjusted for the different shapes and sizes of afacial profile. The angle of the seal relative to the face may beadjusted with this invention. U.S. Pat. No. 6,119,693 is herebyincorporated by cross-reference in their entirety. In InternationalPatent Application PCT/AU00/00097 (WO 00/78384), a forehead support isdisclosed that is adapted to be secured to a respiratory mask.International Patent Application PCT/AU00/00097 (WO 00/78384) is herebyincorporated by cross-reference in its entirety.

[0013] Accordingly, a need has developed in the art to provide a maskassembly that is capable of overcoming the drawbacks or limitations ofthe prior art.

BRIEF SUMMARY OF THE INVENTION

[0014] One aspect of the present invention is directed towards acomfortable patient interface for delivering NPPV therapy.

[0015] Another aspect of the invention is to provide a patient interfacethat will result in improved patient compliance with NPPV therapy.

[0016] It is another aspect of the present invention to create a cushionthat is capable of sealing on a smaller area of the nose as compared toknown masks, while retaining or exceeding the comfort level of theResMed Mirage® and Ultra Mirage® cushions.

[0017] It is a further aspect of the present invention to reduce theperceived and/or actual size and/or weight of a nasal mask and provide aless intrusive mask for the user.

[0018] Another aspect of the present invention is to provide a maskassembly in which the mask and headgear have a reduced amount ofconnections that are provided in a convenient and intuitive location forquick attachment and/or detachment by the patient, while not beingeasily detached accidentally.

[0019] Another aspect of the invention is to provide a mask assembly inwhich it is not necessary to provide a forehead support or an adjustmentmechanism for the forehead support, while maintaining stability of themask in use.

[0020] Another aspect is to provide a nasal mask capable of fitting awide range of patients, so as to decrease or minimize inventoryrequirements and the number of differently sized masks/cushions that arerequired for production.

[0021] Yet another aspect of the present invention is to provide a nasalmask that offers more comfort to the patient, e.g., by better avoidingthe application of unwanted localized pressure points in the facialcontacting regions especially to the sensitive nasal bridge region ofthe patient, while maintaining a good seal, with or without theassistance of positive pressure to form or maintain the seal. Anotheraspect of the present invention is to avoid contact with the upper nasalbridge region, while avoiding localized pressure points along the lowernasal bridge region where the bony portion transitions into a portion ofthe nose containing more cartilage.

[0022] Another aspect of the present invention is to avoid applicationof unwanted localized contact pressure or forces that may increaseundesirably the impedance of airflow through the patient's nares/narisand nasal passages, especially through the nasal vent.

[0023] Still another aspect is to provide a headgear assembly which canprovide added stability to the mask/cushion assembly. In embodiments,the headgear may be made of or include at least one layer which impartsa degree of stiffness to the headstraps to assist in the stabilizationof the mask/cushion assembly, which may obviate the need for a foreheadsupport and thereby decrease visual obstructions near the patient's eyesand better enhance or at least not hinder the patient's ability to don,wear or remove eye glasses with the mask system in use. At least aportion of the headstrap itself may be formed of a relatively more rigidmaterial in comparison to relatively flexible headstraps, instead ofproviding a multiple layer structure. The headgear may include arelatively large, hand-manipulable clip member that can be quickly andeasily attached and/or detached from the head strap and/or the maskframe. Alternatively, the headgear may be magnetically coupled with themask frame.

[0024] Another aspect of the present invention is to provide aconvenient or quick release mechanism which requires little effort ordexterity to operate.

[0025] Another aspect of the present invention is to provide a framewhich includes and/or integrates a quick release mechanism so that theclip member of the head straps can be easily detached from the frame.The quick release mechanism may include at least one connector portionformed in one piece with the frame. A mating connector portion can beprovided on a portion of the headgear. The mask system is attached to asource of pressurized air which is delivered via an air deliveryconduit. The conduit may be directly attached to the mask with its lumenin fluid communication with the mask chamber in order to supplypressurized air to the entrance of the patient's airway. Preferably anintermediate piece connects the air delivery conduit to the mask.Preferably the intermediate piece is an elbow joint, which will bebetter described below. The frame may include an extended tubeprotruding from the outside surface of the mask, which can improve theseal between the elbow joint and the mask frame and also improve thestability of the connection between the mask frame and the elbow joint.The extended tube may include a flange for attachment to the elbowassembly. Preferably the elbow assembly may be easily manipulated toquickly and readily detach the elbow joint from the mask frame during atemporary interruption in patient treatment. The elbow assembly mayinclude a vent to atmosphere. Preferably the vent is in fluidcommunication with the system air path via an exhaust passage which isseparated from the incoming gas path, for example, by using a baffleprovided within a portion of the elbow joint.

[0026] Another aspect of the invention is to provide a generallytrapezoidal shaped mask cushion for a patient interface.

[0027] Another aspect of the invention provides a respiratory maskassembly for delivering breathable gas to a patient. The respiratorymask assembly according to one embodiment includes a frame having afront surface and a rear surface adapted in use to face the patient. Acushion having a side wall is removably attachable to the frame. Thecushion has a rim extending away from the side wall and a membraneprovided to substantially surround the rim. An inner edge of themembrane defines an aperture, the aperture having a generallytrapezoidal shape.

[0028] Of course, portions of the described aspects of the presentinvention may form sub-aspects of the present invention. Also, variousones of the sub-aspects and/or aspects may be combined in variousmanners and also constitute additional aspects or sub-aspects of thepresent invention. These and other features and aspects of the presentinvention will be described in or be apparent from the detaileddescription below read in conjunction with the attached Figures, wherelike reference numerals indicate like components.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings facilitate an understanding of thevarious embodiments of this invention. In such drawings:

[0030]FIG. 1 is a perspective view of a nasal mask assembly according toone preferred embodiment of the present invention;

[0031]FIG. 1b shows a headgear assembly according to an embodiment ofthe invention;

[0032]FIG. 2 is a partial side view of the nasal mask assembly of FIG.1;

[0033]FIG. 3 is a partial front view of the nasal mask assembly of FIG.1;

[0034]FIG. 4 is a partial top plan view of the nasal mask assembly ofFIG. 1;

[0035]FIG. 5 is a front perspective view of a frame component of thenasal mask assembly of FIG. 1;

[0036]FIG. 5a is a top view of the frame of FIG. 5;

[0037]FIG. 5b is a schematic view showing various forces acting on thenasal mask assembly which may affect a patient;

[0038]FIG. 5c is a rear perspective view of the frame of FIG. 5;

[0039]FIG. 6a is a top view of an elbow assembly and frame according toanother embodiment of the present invention;

[0040]FIG. 6b is an exploded view of the embodiment of FIG. 6a;

[0041]FIG. 7 is a partial sectional view of the frame of FIG. 5;

[0042]FIG. 8 is a side view of a left side yoke of the nasal maskassembly of FIG. 1;

[0043]FIG. 8a is an enlarged view of a right side yoke according toanother embodiment of the present invention;

[0044]FIG. 9a is a top view of a locking clip of the nasal mask assemblyof FIG. 1;

[0045]FIG. 9b is a bottom view of the locking clip of FIG. 9a;

[0046]FIG. 10a is a side view of a clip and frame in a nearly fullyconnected condition, according to the present invention;

[0047]FIG. 10b is a bottom view of the clip of FIG. 10a;

[0048]FIG. 10c is a top view of the clip of FIG. 10a;

[0049]FIG. 10d is a perspective view of the clip of FIG. 11a;

[0050]FIGS. 10e-10 g illustrate the clip and yoke of the presentinvention in various connected positions;

[0051]FIG. 11 is a perspective view of a buckle of the nasal maskassembly of FIG. 1;

[0052]FIG. 12 is a bottom view of a cross-over strap of the nasal maskassembly of FIG. 1 in a relaxed state;

[0053]FIG. 13 is a bottom view of the cross-over strap of FIG. 12 in acrossed-over state;

[0054]FIG. 14 is a view of a cross-over buckle of the cross-over strapof FIG. 13;

[0055]FIG. 15 is a perspective view of a strap loop for use with thenasal mask assembly of FIG. 1;

[0056]FIG. 16a is a perspective view of the swivel elbow shown in FIG.1;

[0057]FIG. 16b is a side view of a swivel elbow of the nasal maskassembly of FIG. 1;

[0058]FIG. 17 is a front view of the swivel elbow of FIGS. 16a and 16 b;

[0059]FIG. 18 is a rear view of the swivel elbow of FIGS. 16a and 16 b;

[0060]FIG. 18b is a side view of another embodiment of a swivel elbow;

[0061]FIG. 18c is a front view of the swivel elbow of FIG. 18b;

[0062]FIG. 18d is a rear view of the swivel elbow of FIG. 18b;

[0063]FIG. 18e is a cross-sectional view of the swivel elbow of FIG.18b;

[0064]FIGS. 19a 1-19 c-2 are sequential sectional views of the swivelelbow as shown in FIG. 18, illustrating connection with a flangeextending from the front surface of the frame;

[0065]FIG. 20 is a perspective view of a vent cover of the nasal maskassembly of FIG. 1;

[0066]FIG. 21 is a rear view of the vent cover of FIG. 20;

[0067]FIG. 22 is a bottom view of the vent cover of FIG. 20;

[0068]FIG. 22b is a perspective view of another embodiment of a ventcover for connection with the swivel elbow of FIG. 18b;

[0069]FIG. 22c is a rear view of the vent cover of FIG. 22b;

[0070]FIG. 22d is a bottom view of the vent cover of FIG. 22b;

[0071]FIG. 22e is a side view of the vent cover of FIG. 22b;

[0072]FIG. 22f is a side view of illustrating the vent cover of FIG. 22bconnected to the swivel elbow of FIG. 18b;

[0073]FIG. 23 is a perspective view of a connector tube of the nasalmask of FIG. 6a;

[0074]FIG. 24a is a face side view of a cushion of the nasal maskassembly of FIG. 1 showing Computer Aided Design (CAD) constructionlines;

[0075]FIG. 24b is a frame side view of the cushion of FIG. 24a showingCAD construction lines;

[0076]FIGS. 24c-24 f illustrate various perspectives of the cushionshown in FIG. 24a;

[0077]FIG. 24g shows a mask cushion in accordance with an embodiment ofthe invention incorporating a septum notch;

[0078]FIG. 25a is a perspective view of the cushion shown in FIG. 1showing CAD construction lines;

[0079]FIG. 25b is a face side view of the cushion of FIG. 25a;

[0080]FIG. 25c is a frame side view of the cushion of FIG. 25a showingCAD construction lines;

[0081]FIG. 25d is a cross-section taken along line 25 d-25 d of FIG. 25bshowing CAD construction lines;

[0082]FIG. 25e is a cross-section taken along line 25 e-25 e of FIG.25b;

[0083]FIG. 25f is a cross-section taken along line 25 f-25 f of FIG.25b;

[0084]FIG. 25g is a cross-section taken along line 25 g-25 g of FIG.25b;

[0085]FIG. 25h is a cross-section taken along line 25 h-25 h of FIG.25b;

[0086]FIG. 25i is an enlarged view of FIG. 25d showing typical (TYP)dimensions of an embodiment (R-radius);

[0087]FIG. 26 is a perspective view of an air tube of the nasal maskassembly of FIG. 1;

[0088]FIGS. 27a-27 e are partial sectional views of a frame and cushionof the nasal mask assembly of FIG. 1 showing a sequence of positions ofassembly and disassembly of the frame and cushion;

[0089]FIG. 28 is a partial sectional view of an alternative embodimentof the frame and cushion of the nasal mask assembly of FIG. 1;

[0090]FIGS. 29a-29 d show alternative sealing configurations of thecushion of FIGS. 27a-27 e.

[0091]FIGS. 30 and 31 show various dimensions used to design a maskaccording to FIG. 1;

[0092]FIGS. 32a-1-32 c-2 illustrate an additional embodiment of thepresent invention for engagement between the frame and cushion, thecushion showing CAD construction lines;

[0093]FIG. 32d is an enlarged cross-sectional view of the frame shown inFIGS. 32a-1-32 c-2;

[0094]FIG. 32e illustrates an additional embodiment of the presentinvention for engagement between the frame and cushion;

[0095]FIG. 33 is a perspective view of another embodiment of a frame ofthe nasal mask assembly;

[0096]FIG. 34 is a top view of another embodiment of the yokes of theheadgear assembly of the nasal mask assembly;

[0097]FIG. 35 is an enlarged view of a right side yoke of the headgearassembly shown in FIG. 34;

[0098]FIG. 36 is a perspective view illustrating the frame of FIG. 33magnetically coupled to the headgear assembly of FIGS. 34 and 35;

[0099]FIG. 37 is a schematic view illustrating the magnetic coupling ofthe frame of FIG. 33 and the headgear assembly of FIGS. 34 and 35;

[0100] FIGS. 38A-38D show various perspectives of another embodiment ofthe cushion, the cushion showing CAD construction lines;

[0101] FIGS. 39A-39D show various perspectives of another embodiment ofthe cushion, the cushion showing CAD construction lines;

[0102]FIG. 40 is a perspective view of another embodiment of a frame ofthe nasal mask assembly;

[0103]FIG. 41 is a bottom view of the frame shown in FIG. 40;

[0104]FIG. 42 is a top view of an embodiment of the cushion structuredto be engaged with the frame shown in FIG. 40, the cushion showing CADconstruction lines; and

[0105]FIG. 43 is a rear view of the cushion shown in FIG. 42, thecushion showing CAD construction lines.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0106] Two main embodiments are described in the figures. Although manyof the features and/or parts of each embodiment are the same, there areseveral parts and/or elements that are different. For example, whileFIG. 1 shows one embodiment of an elbow assembly 60 according to thepresent invention, FIGS. 6a-6 b show another arrangement of the elbowassembly 60. Other differences between the embodiments will be describedbelow. Moreover, several alternative approaches are also described withrespect to various parts and/or elements, and those alternativeapproaches should be considered as additional preferred embodiments ofthe present invention.

[0107] As shown in FIGS. 1-4, a nasal mask assembly 10 according to onepreferred embodiment of the present invention includes a frame 20 and acushion 40 that is preferably detachably connected to the frame 20.Alternatively, the cushion 40 can be permanently attached to the frame20 using, e.g., co-molding or over-molding techniques, glue and/ormechanical fastening means. A swivel elbow assembly 60 and a headgearassembly 80 can be attached to the frame 20. FIG. 1 shows the nasal maskassembly 10 generally as it is intended to be mounted onto a human head.Of course, the depiction in FIG. 1 is slightly spaced away from thehead, or “floating”, for ease of understanding. FIG. 1b shows theheadgear assembly laid flat with the frame 20 removed therefrom. FIG. 2illustrates the mask assembly 10 from the left side view, FIG. 3illustrates a front view thereof, and FIG. 4 illustrates a top viewthereof. In FIGS. 2-4, the rear portion of the headgear assembly 80 hasbeen removed for clarity.

[0108] Mask Frame

[0109] As shown in FIG. 5, frame 20 includes an elongated body 22 havinga central bore 24 for connecting to the swivel elbow assembly 60. FIG. 5a is a top view of the frame 20 in which the cushion 40, the elbowassembly 60 and the headgear assembly 80 have been detached. The frame20 includes a main body 20 a, which is designed to accommodate thecushion 40, and a pair of side frame members 20 b that are preferablyformed in one piece with the main body 20 a of the frame 20. FIG. 5ashows that both side frame members preferably have the sameconfiguration. The main body 20 a and the side frame members 20 b havebeen designed to have a curvature that generally follows the facialcontour of the patient's face on each side of the nose. In accordancewith one embodiment of the invention, the curvature follows a smoothtransition from the two side members having an inclusive angle of 120°.With the cushion 40 in place, the main body 20 a is spaced away from thepatient's face in the nose region to prevent contacting the patient'snose, while the side frame members 20 b are generally parallel the cheekregions. A space is maintained between each side frame member 20 b andthe cheek of the patient since contact is not desired in this area.However, if desired, the side frame members 20 b may be constructed toinclude a comfort feature such as pad structure that engages the cheekregions of the patient. Such a pad can have the advantage of assistingin supporting the cheeks when pressure is applied in treatment mode.

[0110] Based on the curved design of the frame 20, and other features,the center of gravity CG1 (FIG. 5b) of the mask assembly 10 can beformed closer to the face of the patient. As such, rotative torque ormoment created in the vertical plane due, for example, to the weight ofthe mask assembly can be reduced. For example, if the patient is sittingin the upright position as shown in FIG. 5b, the weight of the maskassembly 10 can produce torque about an axis A (into the page) that istransverse to the patient's nose in the horizontal plane. That torquecan produce forces tending to rotate the mask assembly 10 in thedirection of arrow B about the axis A which is generally positionedalong the upper lip region of the cushion. Such torque may result inpatient discomfort along the upper lip region and/or reduced sealingaround the lower bridge region of the nose and/or at the cheek region.Specifically, a center of gravity CG1 located close to the face canproduce less torque than a mask having a center of gravity CG2 that isfurther away from the face. This is because the distance d1, d2 betweenthe center of gravity CG1, CG2 and the face defines the lever arm usedto measure torque (torque=force×lever arm distance). Accordingly, torquecan be reduced if the force or the lever arm distance is reduced.Similar torques can be created if the patient is lying on his or herside as well. The torque is affected by the geometry of the elbow,including such features as its length and height in relation to thecushion. It is desirable to minimise the effective lever arm length ofthe assembly which depends amongst other things on the configuration ofthe elbow.

[0111] Other factors which contribute towards reducing the distancebetween the center of gravity of the mask assembly and the face includedesign of the cushion 40, the design of the frame 20, and the design ofthe elbow assembly 60. Another source of torque, which may affectstability of the mask, is the connection of the elbow assembly 60 to thegas delivery tube. In effect, the gas delivery tube may impart a forceon the elbow assembly 60, which in turn may create a torque tending toshift the mask assembly with respect to the patient. The amount oftorque applied to the patient due to the connection between the elbowassembly and the gas delivery tube can be reduced using the elbowassembly 60 discussed below in relation to FIGS. 16a-19 c-2. In short,the lever arm of the elbow assembly can be effectively reduced becausethe elbow assembly is designed to be connected directly to a gasdelivery tube 310 (FIG. 26), without the need for an intermediate swivelconnector member 300 (FIGS. 6b and 23) between the elbow assembly andthe gas delivery tube 310, as is currently used in some prior art.Alternatively, a swivel may be incorporated within the tube. In thisway, an additional degree of freedom of movement may be added withoutincreasing the undesirable torque. Also, because the cushion 40 isdesigned to distribute pressure at least along the lip and cheek regionsof the cushion 40, the possibility or tendency to rotate in the verticalplane is further reduced. Moreover, each of the cheek regions of thecushion 40 defines a relatively large contact pressure receiving surfacethat is elongated in the vertical direction and widened in thehorizontal direction. As such the cushion 40, at least in the cheekregions, resist rotational movement in the vertical and/or horizontalplanes, which helps maintain the cushion 40 in a consistent position onthe patient. More details of the cushion 40 are described below inrelation to FIGS. 24a-25 i. Referring to FIG. 5c, the frame 20 includesa channel 26 having a generally trapezoidal shape for connecting to thecushion 40. The channel 26 includes an inner wall 28, an outer wall 30and a channel floor 32. The channel 26 will be described in furtherdetail below.

[0112]FIG. 6a shows a frame 20 and elbow assembly 60 that is slightlydifferent than the frame 20 and elbow assembly 60 shown in FIGS. 1-5 c.Although the main differences between the embodiments reside in theelbow assembly 60, there are other differences between the frames 20,cushions 40, etc., as will be readily seen by comparing the variousfigures, or understood in conjunction with the description in varioussections below. Like elements are indicated with like reference numbers.

[0113] In FIGS. 6a and 6 b, the elbow assembly 60 is attached to themask 20 using a C-clip 23 (FIG. 6b) that can be expanded and contractedto fit within a circumferal groove 25 provided on a portion of the elbowassembly 60 that protrudes into the frame 20 using a mechanism similarto that provided on ResMed's ULTRA MIRAGE® mask and as described in U.S.patent application Ser. No. 09/594,775 (Drew et al.). An exploded viewof the cushion 40, the frame 20, the elbow assembly 60 and the gasdelivery tube is shown in FIG. 6b. The C-clip 23 has a surface thatengages the inside surface of the frame 20 to prevent unwanteddisconnection between elbow assembly 60 from the frame 20. The elbowassembly 60 may also include one or more vent openings 61 open toatmosphere, for example, for gas washout of exhaled carbon dioxide,among other things. The vent openings 61 are structured so thattreatment pressure will be maintained within the nasal cavity. The ventopenings 61 may be covered with a shell member 65 which is resilientlyand removably clipped onto an outer surface of the elbow assembly 60.The vent openings 61 in FIG. 6a are visible through the clear shellmember 65. Details of the shell member 65 and the C-clip are describedin the ResMed's U.S. patent application Ser. Nos. 09/502,745, 09/594,775or PCT Application No. PCT/AU00/00097 (WO 00/78384), all of which areincorporated herein by reference.

[0114] As shown in FIG. 6a, the inner wall 28 of channel 26 preferablyextends away from the frame 20 to a distance that is greater than thedistance that the outer wall 30 extends away from the frame 20. FIGS. 5cand 32 d also show that the inner wall 28 extends away from the frame 20a distance that is greater than the distance over which the outer wall30 extends away from the frame 20. As shown in FIG. 32d, the thicknessof the inner wall 28 is in the range of about 1-2 mm, preferably 1.4 mm,the thickness of the outer wall 30 is in the range of about 1-2 mm,preferably 1.4 mm, and the distance between the tops of the inner andouter walls 28, 30 is in the range of 0.5-10 mm, preferably 2 mm.Further, as shown in FIG. 32d, the width of channel 26 between theupstanding surfaces of the inner and outer walls 28, 30 that face eachother is in the range of about 2-10 mm, preferably 5 mm.

[0115] By adopting this relative distance between inner wall 28 andouter wall 30, the engagement of the cushion 40 to the frame 20 isfacilitated. As the cushion and mask frame are moved together, the innerwall 28 provides a visual and/or tactile cue to cushion alignment andthen will facilitate the continuance of the engagement process byguiding the edge of the side wall or central portion 215 (FIGS. 24e and27 a) of the cushion 40 into channel 26, as will be more fully explainedwith reference to FIGS. 27a-29 d and 32 a-1-32 c-2. The shape of thechannel 26, e.g., a generally trapezoid shape as seen in FIG. 5c, isselected so as to achieve guidance to correct cushion orientationrelative to the channel 26 without the need for additional guide piecesas would be the case should the channel 26 have a more symmetrical shapesuch as an equilateral triangle, circle, square or rectangle.Nevertheless, the cushion channel 26 could adopt any of these shapes.

[0116] As seen in FIGS. 5c and 6 a, the frame 20 includes a locking clipreceiver assembly 34 positioned on each side of the frame 20 forconnecting to a respective locking clip 82 (FIGS. 9a and 10 a) of theheadgear assembly 80. Each locking clip receiver assembly 34 includes anengagement face 35 (FIG. 5c), a central support slot 36 and two lockingslots 38 positioned on opposite sides of the central support slot 36.The central support slots 36 and locking slots 38 have a generallyrectangular cross-section. Each of the locking slots 38 includes alocking flange 39 (FIG. 7) positioned on an outer wall thereof forengagement with a respective locking tab 116 (FIGS. 9a and 9 b) of oneof the locking clips 82, as described below. The channel 38 may beprovided with a slot 71 (FIG. 10a) in the outer wall of the frame 20 inaddition to or in replacement of the locking flange 39 (FIG. 7). Theslots 71 on the bottom of the frame 20 can be seen in FIG. 5a, whileFIG. 4 shows the slots 71 from the top of the frame 20. The slots 71need not extend through the side walls of the frame 20.

[0117] Headgear Assembly

[0118]FIG. 1b shows headgear assembly 80 in accordance with anembodiment of the invention, without the frame 20 or cushion 40. In FIG.1b, the headgear assembly is shown laid flat.

[0119] The Straps and Yokes

[0120] Referring to FIGS. 1-4, headgear assembly 80 includes a pair offront straps 84, with the left and right front straps 84 preferablybeing mirror images of each other. Each front strap 84 is in the generalform of a “Y” and has a front strap end 86, a top strap end 88 and arear strap end 90 all formed in one piece or otherwise interconnectedtogether by mechanical fastening or the like. The straps are made fromlaminated fabric and foam. One commercially available material is“Breath-O-Prene”™ manufactured by Accumed Inc., USA. Fastening of thestraps may be assisted by use of a hook and loop material such asVELCRO®, however, the straps need not include hook and loop fastenerssince the straps are fastened to the frame 20 using locking clips 82, asmore fully described below. As shown in FIGS. 1-3 and 8, a yoke 92 isattached to each front strap 84. Each yoke 92 has the same general shapeas the corresponding front strap 84 and has a front end 94, a top end 96and a rear end 98. Each yoke 92 is constructed of a somewhat rigidmaterial, e.g., plastic, and has a thickness in the range of 0.3-2.0 mm,preferably 1 mm. Examples of the plastic include nylon 11 orpolypropylene. The yoke 92 is attached to the corresponding front strap84 with adhesives, stitching, or other known attachment mechanisms. Thestrap and yoke arrangement can have different flexibilities in differentdirections, for example being stiff in a first direction (e.g., toresist the deformation due to the weight of the swivel elbow, associatedconduits, etc.), but flexible in a direction generally orthogonal to thefirst direction. Upon donning the mask on the user's head, the relativestiffness of the yokes helps position the frame and cushion in thecorrect position on the user. Although having the same general shape asthe front straps 84, the top ends 96 and rear ends 98 in this embodimentdo not extend as far as the top strap ends 88 and rear strap ends 90 ofthe front straps 84. However, in another embodiment, the top end 96 maybe extended along the entire length of the top strap 88 and be formedintegrally or in one piece with a connector element 128 (FIG. 1). Theyokes 92 are also narrower than the front straps so that when they areattached together, the softer material of the front straps 84 extendsbeyond the more rigid material of the yokes 92, thereby preventing or atleast reducing the opportunity for contact between the user and the morerigid material of the yokes 92 that could cause irritation ordiscomfort. While the straps and associated yokes are formed from amultilayer construction, e.g., two layers, the strap 84 and yoke 92could be formed of a single material, so long as patient comfort and theappropriate rigidity/flexibility are maintained.

[0121] The yokes 92 add to the rigidity of the straps 84 in certainplanes and directions, which assists in stabilizing the mask assembly 10on the head of the patient during use. In other planes and directions,the yoke and strap assembly has a different rigidity. For example, thestrap and yoke should be able to resist bending or curling towards oraway from the patient's face. In general, the strap 84 and yoke 92should be able to maintain their positions with respect to the head ofthe patient when the straps 84 and yokes 92 are connected to the frame20. Moreover, the mask frame 20 need not be provided with a foreheadsupport assembly, which may further increase the comfort of the patientsince the patient's field of view is less obstructed as compared tomasks with forehead supports. Of course, forehead supports of the typedescribed above may be provided if desired for additional stability orcomfort. Also, the mask frame 20 need not be provided with a chin strap,although a chin strap may be provided if desired for additionalstability or comfort. In addition, beyond removal of the foreheadsupport, the shapes of the straps 84 and yokes 92 are selected to avoidinterference with the patient's field of view. In particular whenfitted, the front ends 94 of each yoke 92 are connected to the frame 20below the patient's eyes, and preferably extend along a curved arcresting across the cheek regions. The top end 88 of each strap 84 andthe top end 96 of each yoke extend away from the intersection of the Yalong the temple region of the patient's head. The rear end 98 of theyoke 92 and the rear end 90 of the strap 84 are curved downwardly andaround the ear of the patient for connection with the rear strap member138, as more fully described below. Due to the rigidity provided by theyokes 92, the straps 84 are better able to maintain a predeterminedshape. On the other hand, a certain degree of flexibility of the yoke 92and strap 84 is provided such that variations in patient physiology canbe accommodated to a certain degree. The thickness of the yoke can alsovary across its profile to modify flexibility characteristics, forexample, thicker regions may be stiffer.

[0122] As shown in FIG. 8, each yoke 92 has a mounting flange 100positioned on the front end 94. The mounting flange 100 has an apertureor keyhole 101 leading to a bore 103, see FIG. 8a. Two semi-annularflanges 102 are separated from each other by slots 104. A radial innersurface of the semi-annular flanges 102 forms the central bore 103. Theyoke 92 also has a spring tab 106 positioned rearward of the mountingflange 100 with a front portion of the spring tab connected to the yoke92 and a rear portion separated from the yoke 92 by space 107 to be ableto flex with respect to the yoke 92 when pressure is applied to thespring tab 106. The spring tab 106 preferably has a plurality of raisedteeth 108 positioned in an arc about an axis of the mounting flange 100.The spring tab 106 also has a textured surface 110 (FIG. 8) or a raisedpositioning member 110 a (FIG. 8a) at its free end to assist the user inlocating, engaging and manipulating the spring tab 106. FIG. 8a is anenlarged view of a right side yoke 92 and strap 84, like that shown inFIG. 8, to better show details of yoke 92, including the manner in whichthe yoke 92 is stitched to the head strap 84. Other fixing mechanismssuch as locking or friction may be used.

[0123] The Locking Clip

[0124] The locking clip 82 is adjustably attached to each mountingflange 100. As shown in FIGS. 9a and 9 b, each locking clip 82 includesa main body 112. Two spring arms 114 are attached to opposite sides ofthe main body 112 and extend away from the main body in a generallyparallel manner. A latch hook 116 is attached to a free end of eachspring arm 114.

[0125] As shown in FIG. 10a, the clip 82 can be inserted into releasableengagement with the locking clip engagement receiver 34 of the frame 20.In FIG. 10a, only one clip 82 is shown and the clip 82 is not assembledto the yoke 92. Each latch hook 116 is received within a respectivechannel 38 (FIG. 5c) of the frame. In FIG. 10a, the distal ends of thelatch hooks 116 are shown in a position just before they outwardly flexinto the respective recesses 71 of the channel 38. FIG. 4 shows thedistal ends of the latch hooks in the engaged position within therecesses 71. Of course, the clip 82 or at least the latch hook 116thereof could be formed in the frame 20, and the channel 38 or at leastthe recess 71 could be formed on the strap and/or yoke.

[0126]FIGS. 4 and 10a also show that the outward surfaces of the lockingclip 82 and the frame 20 preferably form a generally continuous surface,which is not interrupted when connected. Preferably, the locking clip 82is as wide as the frame 20 at each end, which facilitates tactilelocation of the locking clip by the patient. The spring arms 114 aredesigned to flex within the plane of the locking clip main body, whichfurther improves the ease by which the locking clips 82 are attached anddetached. This positioning improves the ergonomics of the releasemechanism. The patient's thumb and an opposing finger can be used toreadily locate and operate the locking clips 82. Also, because of theirincreased size, patients with minimal dexterity can operate the lockingclips 82. Further, the locking clips 82 are connected to the strap84/yoke 92 so that length adjustment between the locking clips 82 andthe strap 84/yoke 92 is not necessary.

[0127] The locking clip 82 includes a retaining flange 118 (FIG. 9b)extending transversely outward from the main body 112. The retainingflange 118 has a central hub 119 extending along an axis of theretaining flange 118 and two retaining tabs 120 extending transverselyfrom the central hub 119 on opposite sides of the central hub 119. FIGS.10b-d show more details of the locking clips 82 shown in FIG. 10a, whichare similar to features shown in FIGS. 9a and 9 b. While the lockingclip 82 has been shown to be separate from the yoke 92, it is understoodthat the clip and yoke 92 could be formed in one piece if relativemovement and/or detachment between the two is not required. Conversely,the clip 82 and frame 20 can be formed as an integral unit, and the clipportion could be connected to the yoke.

[0128] The retaining flange 118 is sized and shaped such that theretaining tabs 120 can be aligned with the slots 104 and the retainingflange 118 axially inserted into the mounting flange 100 of the yoke 92.The central hub 119 is sized to have a close tolerance with the centralbore 103 so that the locking clip 82 and yoke 92 are rotationallysupported with one another. Once the retaining flange 118 has beeninserted into the mounting flange 100, the locking clip 82 can berotated with respect to the yoke 92 such that the retaining tabs 120engage an inside surface of the flanges 102, thereby axially locking themounting clip 82 to the yoke 92. FIGS. 10e-g show the locking clip 82 invarious positions with respect to the yoke 92. In FIG. 10e, the tabs 120of the clip 82 have been inserted through the openings 104 of the yoke92, and the clip 82 has been rotated slightly along the direction ofarrow A such that the upper surfaces of the tabs 120 snugly engage theinside surfaces of the semi-annular portions 102. When the clip 82 isattached such that the flexing arms 114 are positioned approximately 90degrees with respect to the front end 94 of the yoke 92, the clip 82 canbe removed from the yoke 92. In this embodiment, there are two positionsin which the removal can occur, and both of these positions are selectedsuch that they would not occur when the mask is in normal use; otherwisethe clips 82 could be inadvertently detached from the yokes 92. FIGS.10f and 10 g show the clip 82 in different rotational orientations withrespect to the yoke 92.

[0129] As seen in FIGS. 9b and 10 b, the locking clip also has aplurality of raised teeth 122 positioned in an arc about an axis of theretaining flange 118. The teeth 122 are constructed and arranged so asto engage the teeth 108 on spring tab 106. Once the spring tab 106 hasbeen depressed to lower teeth 108, the locking clip 82 can be rotated toa desired position with respect to the yoke 92. The spring tab 106 canthen be released so that teeth 108 engage teeth 122 in the desiredposition (within a pitch of the teeth) and rotationally lock the lockingclip 82 with respect to the yoke 92. In accordance with one embodiment,the teeth 108 and 122 can be configured so that when a predeterminedtorque is applied to the locking clip 82, the teeth 122 willautomatically force the teeth 108 and spring tab 106 downwardly to allowrotation of the locking lip 82 until the torque is removed and the teeth108 re-engage the teeth 122. The locking clip 82 can thus berotationally adjusted with respect to the yoke 92 within an angle ofapproximately 50-100°, and preferably 75°, depending on the position ofengagement between teeth 108 and teeth 122. The angle of availablerotational adjustment can be altered as desired by altering the numberand positioning of teeth 108 and 122. The adjustment angle rangereflects the relative cushion positions required on the face. Rotationaladjustment with a toothed system as described above allows easyadjustment by the patient and allows a broad range of positions toaccommodate a wide range of patients' faces. For example, the patientmay adjust both locking clips 82 to have the same angle with respect tothe yokes 92. Alternatively, the patient may adjust the locking clips 82such that the locking clips 82 have different respective angles withrespect to the yokes 92. The toothed system allows the patient to easilyset and reproduce the desired angle for each locking clip 82. Forexample, the toothed system may allow relative movement between eachlocking clip and its respective yoke in, for example, five positions,which should accommodate most faces. Of course more or less than fivepositions could be used instead, depending on application. Moreover,once it is determined that a particular angle for each locking clip 82with respect to the yokes 92 is desired, the mask system may include anonadjustable clip arrangement which fixes the rotational position ofthe locking clips 82 with respect to the yokes 92. The teeth are largeenough for the patient to easily determine the relative positions of thelocking clip with respect to the yokes.

[0130] Further, the spring tab 106 is configured and positioned suchthat the patient cannot inadvertently depress the spring tab 106, e.g.,by rolling over on the locking clip/yoke during sleeping, to cause thelocking clip 82 to move relative to the yoke 92. For example, as shownin FIGS. 10e-10 g and FIG. 36 (a different embodiment), the locking clip82 extends further outwardly from the yoke 92 than the spring tab 106.That is, the spring tab 106 is positioned lower than the outer edge ofthe locking clip 82. Thus, the positioning of the locking clip 82 withrespect to the spring tab 106 prevents inadvertent actuation of thespring tab 106. Moreover, the spring tab 106 is connected to the yoke 92such that the yoke 92 can flex toward and away from the spring tab 106without disengaging the teeth 108 of the spring tab 106 from the teeth122 of the locking clip 82.

[0131] Alternative adjustment assemblies may be achieved by simplereversal of some or all of the sub-assemblies. For example, the centralhub 119 might be located on the yoke 92 while its reciprocal yokecentral bore 103 may be located on the locking clip 82. In a similarway, each sub-assembly and its reciprocal may be reversed.Alternatively, the yoke 92 and locking clip 82 may be adjustablyconnected by way of a screw or clamping mechanism, e.g., a part that maybe separate from the yoke and clip, which can be used to selectivelyconnect the yoke 92 and clip 82 in a plurality of desired positions. Inaddition, the central bore 103 can be shaped in any manner that allowsdetachment and attachment between the yoke and the clip. Also, a systemof replacement yokes that would allow a fixed angle with respect to thelocking clip may be used.

[0132] The locking clip 82 also includes a central support tab 124extending outward from the main body 112 between and generally parallelto spring arms 114. The central support tab 124 is configured to have aclose fit with the central support slot 36, so that when the centralsupport tab 124 is inserted into the central support slot 36, littlerotational, rocking or side to side movement is permitted between thelocking clip 82 and the locking clip receiver assembly 34. Centralsupport tab 124 is longer than arms 114 to assist with alignment intothe frame. The locking clip 82 also has an engagement face 125 thatengages engagement face 35 (FIG. 5c) when the locking clip 82 isinserted into the locking clip receiver assembly 34 to provideadditional support for the locking clip 82. The latch hooks 116 and/orthe central support tab 124 may have tapered widths and/or thicknessesto facilitate entry into slots 36, 38. Also, the latch hooks 116 and/orcentral support tab 124 may have rounded or contoured edges tofacilitate entry into slots 36, 38. Further, the central support tab 124may have a groove that engages a protrusion provided in the centralsupport slot 36 to facilitate entry of the central support tab 124 intothe central support slot 36. Alternatively, the central support tab 124may have a protrusion that engages a groove provided in the centralsupport slot 36.

[0133] When the locking clip 82 is inserted into the locking clipreceiver assembly 34, the spring arms 114 are forced toward one anotheras the latch hooks 116 are inserted into recesses 71 (FIG. 4) or ride upand over the locking flanges 39 (FIG. 7). Once the latch hooks 116 havecleared the locking flanges 39 or recesses 71, the spring arms 114 canspring outward, providing a locking engagement between the latch hooks116 and the locking flanges 39 and/or recesses 71. Sufficient clearanceis provided in locking slots 38 to allow the necessary movement of thelatch hooks 116 to clear the locking flanges 39.

[0134] In this manner, the respective left and right front strapassemblies, including front straps 84, yokes 92 and locking clips 82,can be attached to the frame 20 and the yokes 92 and front straps 84rotationally adjusted with respect to the frame 20 within an angle ofapproximately 50-100°, and preferably 75°.

[0135] In a preferred embodiment, the locking clip 82 is a unitaryplastic piece formed by injection molding. Examples of the plasticinclude nylon, acetal, polycarbonate, and polypropylene. In oneembodiment, the retaining tabs 120 are formed during the molding processby mold projections that leave bores 126 extending through the main body112 of the locking clip 82, thereby separating under surfaces of theretaining tabs 120 from the main body 112.

[0136] Magnetic Interconnection

[0137] FIGS. 33-37 illustrate an alternative embodiment for removablycoupling the frame 420 and the headgear assembly 480. Specifically, theframe 420 and the yokes 492 are structured such that the yokes 492 maybe magnetically coupled to the frame 420.

[0138] As shown in FIG. 33, the frame includes a main body 420 a and apair of side frame members 420 b. Similar to the embodiment of frame 20,the main body 420 a is structured to be removably coupled with thecushion 40. Each side frame member 420 b includes a first connectorportion 434 for connecting to a second connector portion 435 provided bythe yoke 492 of the headgear assembly 480. In the illustratedembodiment, the first connector portion 434 includes a retainingstructure 418 that extends outwardly from the side frame member 420 b.The retaining structure 418 is structured to retain a magnet 419. In oneembodiment, the magnet 419 is constructed of Neodymium and has acylindrical shape with a diameter of 6.35 mm and a thickness of 6.35 mm.However, the retaining structure 418 may be structured to retain amagnet of any suitable size and shape. Further, the outer edges of theside frame members 420 b each include a plurality of raised teeth 422positioned in an arc.

[0139] As shown in FIGS. 34 and 35, the yokes 492 of the headgearassembly 480 each include structure that is similar to the yokes 92 ofheadgear assembly 80. Specifically, the yokes 492 each include thesecond connector portion 435 having a mounting flange 400 positioned onthe front end 494 thereof. The mounting flange 400 has an aperture orkeyhole 401 leading to a bore 403. Two semi-annular flanges 402 areseparated from each other by slots 404. A radial inner surface of thesemi-annular flanges 402 forms the central bore 403. The yoke 492 alsohas a spring tab 406 positioned rearward of the mounting flange 400 witha front portion of the spring tab 406 connected to the yoke 492 and arear portion separated from the yoke 492 by space 407 to be able to flexwith respect to the yoke 492 when pressure is applied to the spring tab406. The spring tab 406 preferably has a plurality of raised teeth 408positioned in an arc about an axis of the mounting flange 400. Thespring tab 406 also has a raised positioning member 410 at its free endto assist the user in locating, engaging and manipulating the spring tab406.

[0140] In contrast to the yoke 92, the yoke 492 includes a ferrous metaldisk 412 that is secured within the bore 403. In one embodiment, themetal disk 412 is a steel washer with a diameter of 14 mm and athickness of 1 mm. However, the metal disk 412 may have any suitablesize and shape that can be mounted within the bore 403 of yoke 492.Further, a magnet of suitable size and shape may be used in place of themetal disk 412.

[0141] As shown in FIGS. 36 and 37, the first connector portion 434 ofthe frame 420 is engaged with the second connector portion 435 of theyoke 492 such that the magnet 419 is magnetically coupled with the metaldisk 412. Specifically, the magnet 419 is axially inserted into the bore403 so that the magnet 419 is positioned adjacent to or engaged with themetal disk 412 which allows the magnetic attraction between the magnet419 and the metal disk 412 to axially retain the yoke 492 to the frame420. The strength of the magnetic attraction between the yokes 492 andthe frame 420 may be increased by replacing the metal disk 412 with amagnet, as discussed above. The retaining structure 418 is sized to havea close tolerance with the bore 403 so that the frame 420 and yoke 492are rotationally supported with one another.

[0142] Further, the teeth 422 on the frame 420 are constructed andarranged to engage the teeth 408 on the spring tab 406 when the frame420 is magnetically coupled with the yoke 492. Once the spring tab 406has been depressed to lower teeth 408, the yoke 492 can be rotated to adesired position with respect to the frame 420. The spring tab 406 canthen be released so that teeth 408 engage teeth 422 in the desiredposition (within a pitch of the teeth) and rotationally lock the frame420 with respect to the yoke 492. In accordance with one embodiment, theteeth 408 and 422 can be configured so that when a predetermined torqueis applied to the yoke 492, the teeth 422 will automatically force theteeth 408 and spring tab 406 downwardly to allow rotation of the yoke492 until the torque is removed and the teeth 408 re-engage the teeth422. The yoke 492 can thus be rotationally adjusted with respect to theframe 420 within an angle of approximately 50-100°, and preferably 75°,depending on the position of engagement between teeth 408 and teeth 422.

[0143] The magnet 419 in each side frame member 420 b may be orientedsuch that an incorrect attachment (e.g., left side yoke 492 to rightside frame member 420 b) is indicated by magnetic repulsion.Specifically, the magnet 419 on one side frame member 420 b is orientedso that it will only magnetically couple with one of the yokes 492 andthe magnet 419 on the other side frame member 420 b is oriented so thatit will only magnetically couple with the other of the yokes 492. Thus,sensory indication of correct attachment of the frame 420 to theheadgear assembly 480 is achieved by magnetic attraction of correctlypaired yokes 492 and side frame members 420 b. This construction ensuresthat the headgear assembly 480 and frame 420 are assembled correctly.Further, this construction enables the frame 420 to be easily coupledwith the headgear assembly 480, even in the dark, as the magnet 419 willautomatically locate itself in the correct position with respect to themetal disk 412. The headgear assembly 480 may be easily detached fromthe frame 420 by applying a suitable disengagement force that is greaterthan the attractive magnetic force between the magnet 419 and the metaldisk 412.

[0144] Alternatively, the first connector portion 434 on the frame 420may provide a ferrous metal member and the second connector portion 435on the yoke 492 may provide a magnet.

[0145] Straps

[0146] Each front strap 84 includes a ladder-type buckle 128 attached tothe top strap 88 to connect the top strap 88 with a top strap 140 ofcross-over strap 138. See FIGS. 1-3 and 11. The buckle 128 can beattached to the top strap 88 with adhesives, stitching and/or otherknown manners, such as being manufactured integral with the strap. Inthe embodiment shown in FIG. 11, the buckle 128 includes a plurality ofbores 130 evenly spaced around an attachment tab 132 in the form of asquare to allow the buckle to be stitched to the top strap 88. Thebuckle further includes a crossbar 134 and a crossbar 136, around whichthe top strap 140 can be threaded, in a known manner, so that top strap140 wraps around crossbar 136 and a free end of top strap 140 ispositioned between crossbar 134 and a remainder of top strap 140. Thus,when tension is applied between the buckle 128 and top strap 140, thefree end of top strap is frictionally held between crossbar 134 and theremainder of top strap 140 so that the connection between buckle 128 andtop strap 140 is self holding under tension. A single cross bar bucklecan also be used if used in combination with a strap loop to hold thestrap in position. Of course, other connector members can be usedinstead of the buckle, as is known in the art.

[0147] As shown in FIG. 12, cross-over strap 138 has a generallyelongated shape in a relaxed state with two top straps 140 extendingupward from a cross-strap 142 having ends 144. To place the cross-overstrap 138 in a configuration for wearing, the two top straps 140 arethreaded through a crossover buckle 146, so that they are held in thecross-over position. See FIGS. 13 and 14. In this manner, the left topstrap 140 of cross-over strap 138 crosses over to connect with thebuckle 128 of right top strap 88 and the right top strap 140 ofcross-over strap 138 crosses over to connect with the buckle 128 of lefttop strap 88. This crossing over of the respective straps helps maintainthe headgear assembly 80 and nasal mask assembly 10 in a desiredadjusted position on the user. A strap loop 148 can be used to hold downfree ends of the respective straps. See FIG. 15. In one form of theinvention, the straps are supplied oversized and then cut to length tosuit the person.

[0148] Similarly to buckles 128 and top straps 88, buckles 150 (FIG. 1)can be attached to cross-strap ends 144 so that the cross-strap ends 144can be connected to the respective rear strap ends 90 of front straps84.

[0149] Swivel Elbow Assembly

[0150] The swivel elbow assembly 60 of FIG. 6a may be the same as iscurrently used in ResMed Limited's ULTRA MIRAGE® mask, which employs aninternal C-clip member, as described above. The elbow assembly 60 ofFIG. 6a is intended to be used with a connector tube 300 (FIG. 23). Theconnector tube 300 is provided between the elbow assembly 60 and the gasdelivery tube 310 (FIG. 26).

[0151] Alternatively, the swivel elbow assembly may be constructed inaccordance with FIGS. 1-4 and 16-22. Such a swivel elbow assembly 60 mayinclude a swivel elbow 160 and a vent cover 180. Swivel elbow 160 isrotationally connected to frame 20.

[0152] In another alternative form of the invention, a further swivel isconnected to the end of tube 310, as shown in FIG. 6b.

[0153] As shown in FIGS. 16a-19 c-2, swivel elbow 160 includes an intakeport 162 and an exhaust port 164. The air tube 310 (FIG. 26) ispreferably directly connected to a stem 166 of swivel elbow 160 (withoutconnector tube 300) to supply pressurized breathable air or gas from apressurized supply through air tube 310, intake port 162 and intocushion 40 for breathing by the patient.

[0154] The exhaust port 164 is separated from the intake port 162 using,for example, a baffle 161 provided within the interior portion of theelbow 160. See FIGS. 18 and 19a-1. In the illustrated embodiment, thebaffle 161 has a generally planar configuration. However, the baffle 161may have a curved configuration or any other suitable configuration forseparating the exhaust port 164 from the intake port 162. Theorientation of the intake and exhaust ports 162, 164 was selected suchthat the incoming gas, indicated by the directional arrow in the intakeport 162, less directly impacts the flow of gas washout along theexhaust port 164. Further, the gas entering the elbow 160 is less likelyto flow directly into the exhaust port 164 since the baffle 161 forcesthe incoming air to take a tortuous path, e.g., turn around about 180degrees, before being able to exit through the exhaust port 164.

[0155] The elbow 160 includes an end portion 169 that is adapted toengage the aperture 24 provided in the frame 20, to provide gas into thenasal cavity formed by the frame 20 and the cushion 40. The baffle 161terminates just inside the end portion 169 of the elbow. A flexiblequick release mechanism includes a collar 173 and an apron 170. Thecollar 173 includes a generally T-shaped member, as seen in FIG. 16b,that surrounds the end portion 169 of the elbow 160. Preferably, the endportion 169 of the elbow 160 extends beyond the collar 173 to improvealignment when assembling into frame 20. The collar 173 is spaced awayfrom the end portion 169 in concentric relation so as to form areceiving space 183 between the collar 173 and the end portion 169, asshown in FIG. 18. The apron 170 is preferably formed as an integral partof the elbow 160, and is connected to the lower leg of the T-shapedcollar 173. Two grooves 167 are provided between the collar 173 and theapron 170. A portion 167 a of the groove 167 allows the lower leg of theT-shaped collar 173 to flex with respect to the apron 170. A portion 167b of the groove allows the cross portion of the T-shaped collar 173 toflex outwardly and inwardly with respect to the end portion 169 of theelbow 160.

[0156]FIGS. 19a-1-19 c-2 show sequential views illustrating connectionbetween the elbow 160 and the frame 20. FIGS. 19a-1-19 a-2 show a crosssection of the elbow 160 just before connection with the mask frame 20.FIGS. 19b-1-19 b-2 show the elbow 160 and frame 20 in the nearlyconnected condition, and FIGS. 19c-1-19 c-2 show the elbow and frame inthe fully connected condition.

[0157] The frame 20 includes a flange 21 provided at a distal end of awall 25 defining the aperture 24. FIGS. 5 and 5a show the flange 21,while the embodiment of FIG. 6a does not show or include such a flangesince a different elbow assembly 160 is employed. As the flange 21 isinserted within the space 183, it engages protrusions 181 formed in theinside surface of the collar 173. In this embodiment, only twoprotrusions 181 are provided. The protrusions 181 are ramped or inclinedsuch that engagement with the flange 21 causes outward flexure (FIGS.19b-1-19 b-2) of each end of the cross portion of the T-shaped collar173, until the flange 21 aligns with and is received within the grooveportion 167 b (FIGS. 19c-1-19 c-2). In this state, with the elbow 160secured to the frame 20, the collar 173 returns to its unflexed state.Portions of the flange 21 rest against lugs 165 provided within thespace 183.

[0158] The engagement between the collar 173 and the flange 21 duringthe snap-action connection of the elbow 160 and the frame 20 results inan audible click or sound indication. This sound indication isadvantageous to signal the user that the elbow 160 is securely attachedto the frame 20.

[0159] To release the elbow 160 from the frame 20, portions 185 on eachside of the collar 173 are flexed towards one another in order to raisethe protrusions 181 radially outwardly to allow passage of the flange21. In this manner, the elbow 160 can be quickly and easily removed fromthe frame 20 without accessing the interior portion of the nasal cavity,as would be the case with an elbow connected using a C-clip (FIG. 6b).As shown in FIG. 16b, a preferred form of the elbow 160 includestextured protrusions 185 to assist users to locate the release points.The distance between the opposed textured portions 185, i.e., thediameter of the collar 173, is approximately 35-45 mm, and preferably 40mm.

[0160] The elbow 160 also is adapted to connect directly to the gasdelivery tube 310 (FIG. 26) without the connector 300 shown in FIG. 23.(See FIG. 1). FIG. 6b shows the connector 300 between the elbow and thegas delivery tube 310. Removal of the connector 300 is advantageousbecause the length of the effective lever arm of the combined elbow andconnector 300 (FIG. 6b) may increase the possibility that unwantedlevels of torque are applied to the frame 20 or mask assembly 10relative to the patient's head/face. By eliminating the need to use theconnector 300, the effective length of the level arm can be reduced,which results in less torque being applied to the mask assembly whichresults in increased stability. With increased stability, patientcomfort is increased and compliance is increased.

[0161] In the connected state, the inside surface of the wall 25 of theframe 20 sealingly engages the outside surface of the end portion 169 ofthe conduit as shown in FIGS. 19a-1-19 c-2. These surfaces engage oneanother for a distance of approximately 1-10 mm, preferably 6 mm, whichhelps to seal as well as to provide stability to the connection betweenthe elbow 160 and the frame 20. As seen in FIGS. 19c-1-19 c-2, a portionof the wall 25 extends inside the mask 20 to further increase the areaof contact between the elbow 160 and the frame 20. In the connectedstate, an end portion 173 a of the collar 173 is flush with the outsidesurface 20 c of the frame 20, as shown in FIGS. 19c-1-19 c-2. The wall25 includes a flange 25 a (FIGS. 19c-2) to form a stop for the insertionof the end portions 169, and to permit a controlled leak between theelbow 160 and frame 20. In one embodiment, the leak between the elbow160 and frame 20 is minimal. In another embodiment, a seal is providedbetween the elbow 160 and frame 20 to prevent a leak.

[0162] This system allows for the rapid and precise connection betweenthe elbow 160 and the frame 20. It also allows for simple disassembly.Moreover, the elbow 160 is configured to allow the patient to attach anddetach the elbow 160 from the frame 20 with one hand. This isadvantageous when cleaning the mask or if the patient should choose tointerrupt treatment during a session, while intending to resumetreatment a short time later. The elbow assembly 60 and frame 20connection allows the patient to rapidly disconnect the elbow 160 fromthe blower's gas delivery tube while keeping the mask frame, cushion andheadgear in place on the patient's head during a momentary treatmentinterruption. The aperture 24 is large enough to lower impedance, tothereby enable the patient to breathe comfortably since a sufficientamount of gas can be accommodated by the aperture 24. Specifically, theaperture 24 has an area of at 2 least 180 mm. In one embodiment, theaperture 24 has a diameter in the range of 20-30 mm, preferably 27 mm,and an area in the range of 200-600 mm², preferably 2 in the range of500-600 mm². As illustrated, the aperture has a generally circularshape. However, the aperture may have a non-circular shape. Further, theframe may have a plurality of apertures therethrough with the elbowcoupled to the frame such that it surrounds the plurality of apertures.In this respect, a mask in accordance with an embodiment of theinvention differs from prior art mask arrangements which included quickrelease mechanisms with narrower apertures. Such narrower aperturedquick release mechanisms could lead to patient discomfort, for exampleanxiety or claustrophobia. Discomfort is exacerbated by increased CO₂re-breathing or increased flow impedance.

[0163] Vent Cover

[0164] Vent cover 180 includes a main body 182 having a lower bore 184,curved portion 186 and top portion 188. See FIGS. 20-22. The main body182 also includes at least one vent 190, and in a preferred embodiment,a plurality of vents 190 extending from an interior of the vent cover toan exterior of the vent cover. Top portion 188 of vent cover 180includes flange or aperture 192 for engaging latch 168 of swivel joint160. In the illustrated embodiment, the vent cover 180 includes anaperture 192. The vent cover 180 is connected to the swivel joint 160 byplacing the stem 166 of the swivel joint 160 through lower bore 184 ofthe vent cover 180. The vent cover 180 is then moved toward the swiveljoint 160 until the latch 168 extends through the aperture 192, as shownin FIG. 1. This configuration allows for the vent cover 180 to remain inthe vicinity of the elbow assembly 160 and/or mask assembly 10, as it iscaptured by the elbow 160 or the gas delivery conduit. This isconvenient in that should the vent cover 180 become dislodged duringcleaning or by inadvertence, it will not drop and become lost, as it isretained by the mask assembly.

[0165] The curved portion 186 of the vent cover fits adjacent apron 170of the swivel joint 160 to provide a generally air-tight seal between aninterior of the vent cover 180 and the swivel joint 160. In this manner,exhalation gases from an interior of the mask can flow through exhaustport 164 of swivel joint 160, through the interior of the vent cover 180and to the atmosphere through vents 190. FIGS. 19c-1 includes an arrow Bthat approximates the path exhaust gas follows when the vent cover is inposition. This arrangement has an additional advantage in that the ventdirection reduces or prevents irritation of a bed partner of the patientby gas flow from the mask. FIGS. 1-4 show the elbow 160 and vent cover180 in the connected position. A spacer 163 is provided to ensure thatthe vent cover 180 is spaced sufficiently away from the exterior surfaceof the elbow 160, which especially helps prevent the air gap fromcollapsing since the vent cover is preferably made of a resilientflexible material. Of course, the vent cover could be made of a plasticmember somewhat like the cover used in the Ultra Mirage™, if desired. Inaddition, this vent arrangement can be replaced or supplemented usingResMed's vent assembly disclosed, for example, in U.S. patentapplication Ser. No. 09/021,541, incorporated herein by reference in itsentirety.

[0166]FIGS. 18b-18 e illustrate another embodiment of the swivel elbow,indicated as 360, that is adapted to be connected to the vent cover 380illustrated in FIGS. 22b-22 e. As shown in FIGS. 18b, 18 c, and 18 e,the swivel elbow 360 includes a flange 361 provided at a distal end of awall 362 surrounding the outlet of the exhaust port 364. FIGS. 18d and18 e show the intake port 365, the exhaust port 364, and a baffle 369that separates the intake and outlet ports 365, 364. As illustrated inFIG. 18e, the baffle 369 has a curved configuration. Specifically, thebaffle 369 curves generally downwardly as it extends from the inlet ofthe exhaust port 364 to the outlet of the exhaust port 369. However, thebaffle 369 may have a generally planar configuration similar to baffle161 shown in FIGS. 19a-1. Alternatively, the baffle may have any othersuitable configuration to separate the intake and outlet ports 365, 364.As shown in FIGS. 22b-22 e, the vent cover 380 includes a main body 382having a lower bore 384, an intermediate portion 386 and top portion388. The main body 382 also includes a plurality of vent holes 390extending from an interior of the vent cover to an exterior of the ventcover. The top portion 388 of the vent cover 380 includes a collar 392for engaging the flange 361 of swivel elbow 360. The vent cover 380 isconnected to the swivel elbow 360 by placing the stem 366 of the swivelelbow 360 through lower bore 384 of the vent cover 380. The vent cover380 is then moved toward the swivel elbow 360 until the collar 392latches onto the flange 361 of the swivel elbow 360. The collar 392 isstretched to overcome the flange 361, and firmly grips the flange 361due to its resiliency and elasticity. In the illustrated embodiment, thecollar 392 has a generally circular shape so that stress (“hoop stress”)applied to the flange 361 and wall 362 is evenly distributed. Similar tothe embodiment of vent cover 180, this configuration allows for the ventcover 380 to remain connected on in the vicinity of the swivel elbow 360and/or mask assembly, as it is captured by the elbow 360 or the gasdelivery conduit. The vent cover can be considered “self-holding” inthat it can be held in place on the elbow to cover the exhaust passagewithout an additional securing mechanism. In addition, the vent cover isheld onto the elbow via the ring-shaped lower bore 184 as the patientstretches the collar 392 over the flange 361, which minimizes thechances for losing the vent cover if the first assembly attempt is notsuccessful.

[0167]FIG. 22f shows the swivel elbow 360 and vent cover 380 in theconnected position. As shown in FIGS. 18c and 18 e, the swivel elbow 360includes a wall 363 that ensures that the vent cover 380 is spacedsufficiently away from the exterior surface of the swivel elbow 360,which especially helps prevent the air gap from collapsing since thevent cover 380 is preferably made of a resilient flexible material. Thevent cover 380 includes a recess 389 (FIG. 22c) on an inner surface ofthe top portion 388 that engages the wall 363.

[0168] Mask Cushion

[0169] The cushion is designed to rest on the face and apply pressurearound its perimeter while minimizing and/or avoiding contact withpressure sensitive regions on the face. Some parts of the face requirespecial attention to achieve a balance of pressure and seal. It is alsodesirable to provide a low profile mask to improve patient comfort levelby improving stability, and to reduce the forces which may tend to pivotthe mask relative to the patient's face. Properties are listed belowwith the measures taken to create a successful design.

[0170] The cushion has a face-contacting side and a non face-contactingside with a wall therebetween. The non-face contacting side of thecushion engages with the mask frame. In one form of the invention, theshape of the cushion on its face-contacting side, as per the view shownin FIG. 24c, is generally trapezoidal. In this aspect, the shape of thecushion on the face contrasts with prior art cushions having a generallytriangular shape. An advantage of this trapezoidal shape is that itassists sealing at a point lower down the nose without impeding flowthrough the patient's or user's nasal vents (that is, in the region ofthe lateral nasal cartilage and just below the nasal bone on either sideof the nose). Thus, the cushion is positioned on a lower portion of thenasal bridge region of the patient. Moreover, the cushion is configuredand positioned such that contact pressure of the cushion on the nasalvents is minimized or eliminated. The shape of the cushion may bealtered, e.g., a triangular or other non-trapezoidal shape could beused, keeping in mind that localized pressure points on the lower nasalbridge region and occlusion of the nasal vents should be avoided. Someprior art mask cushions push on the nasal vents which can increase theimpedance of the nasal vents to airflow. In a preferred form of thecushion, both the face-contacting and non face-contacting sides of thecushion have the same general trapezoidal shape.

[0171] In one form of the invention, a combination of support structureand sealing structure is provided in the region of the face contactingside of the cushion. The support and sealing structures may be providedas part of the cushion, or alternatively using separate components.Where the support and sealing structures are provided as part of thecushion, the cushion may have a single-walled, double-walled or triple-or more walled construction. In a preferred form of cushion, the sealingstructure is provided by a thin membrane, whereas the support structureis provided by a thicker frame.

[0172] The center and sides of the nasal bridge are particularlysensitive to contact pressure. Thus, it is important that the cushionseals as lightly as possible in this area. Instability of the cushionmay cause an increased pressure in the nasal bridge region and thuspresents an extra challenge in this area. The supporting element (e.g.,frame 200 shown in FIG. 24a) can be designed to totally avoid contactwith the adjacent portion of the overlying face-contracting element(e.g., membrane 205 shown in FIG. 24a), thereby allowing the membrane205 alone to seal. While localized points of contact pressure should beavoided in the nasal bridge region, especially at the sensitive apexthereof that contacts the lower nasal bridge region, the seal must bemaintained. The lower nasal bridge region is positioned generally wherethe bony region of the nasal bridge transitions to a portion of the nosecontaining more cartilage. In addition, the forces that are applied tothe face should be substantially evenly distributed around the entireperimeter of the cushion 40. An aspect of the invention is that thefacial contact pressure is controllably distributed around the face. Ofcourse, the forces applied to the lower nasal bridge region can bespread out along a relatively wider section of the membrane 205, toavoid the localized forces, while the forces in the lip and cheekregions can be slightly more localized, e.g., spread out over lessdistance in the width direction, since forces can be more comfortablyaccommodated in the lip and, particularly, in the cheek regions.Moreover, the contact area or width between the membrane and the face inthe lower nasal bridge region may be greater than the contact area orwidth between the membrane and the lip and cheek regions, whilemaintaining a relatively constant overall force distribution around theface of the patient, which improves comfort. Using this arrangement, thepatient perceives that the pressure is evenly distributed over thecontact region, even though the actual force over the contact region maynot be evenly distributed.

[0173] Another advantage is that the angle of the cushion with respectto the patient can change without adversely affecting sealingefficiency. For example, the cushion may contact different patients atdifferent angles based on the shape of the patient's face, and the angleof the cushion can move with respect to the face during movement whenthe patient is asleep.

[0174] The sealing element (e.g., membrane 205) incorporates a largeeffective rolled over section (large radius) to allow some degree ofmovement or rotation of the mask relative to the patient's face andprevents the membrane distal edge from irritating the patient's faceand/or nose. The sealing element (e.g., membrane) snugly seals againstthe nose by conforming around a lower portion of the nasal bridge atsides of the nose. A compromise must be reached between a secure sealand membrane tightness/stretching across the nose. The membrane cutoutcan be notched to enable maximum stretch distance without edgetightness. Stretch can also be achieved by materials, for example softermaterial and or thinner materials, for example, elastomer, silicone,polyurethane, thermoplastic elastomers, foamed elastomers and/orcomposites.

[0175] The sealing element (e.g., membrane) is preferably elastomerichaving a thickness in the range of 0.1 and 2.0 mm, preferably 0.35 mm,to allow the membrane to stretch readily over the lower portion of thenasal bridge. The stretch of the membrane may be varied in differentregions by varying its thickness, adding stiffening structure such asribs, or using composites.

[0176] Facial wrinkling is most pronounced at the facial or nasal creasebetween the sides of the nose (also known as the naso labial sulcus) andthe check and presents a challenge in effective sealing. The underlyingcushion (e.g., frame 200 shown in FIG. 24a) sits as close to the sidesof the nose as possible. In this way it seals in the flattest areapossible. The curved area designed to sit in the facial crease shouldhave as small a radius as is practical. The membrane 205 extendsinwardly and/or downwardly further than the edge of the cushion (e.g.rim 225) to allow rolling around the outer edge at the sides of thenose. This lessens the likelihood of irritation arising from rough edgesand prevents the inner cushion rim 225 from being a source of irritationagainst the patient's face and/or nose.

[0177] Excess pressure across the top lip can be caused by both cushiondesign and by the vertical rotation of the mask under its own weight, orby undesirable force applied to the mask, for example, due to tubingdrag or the weight of components attached to the mask. The design of theheadgear, as described above, can help reduce the possibility of addingunwanted pressure to the lip region due to vertical rotation of the maskunder its own weight. The lip region 42 may include a notch toaccommodate the bottom of the septum of the patient, to enhance sealingand comfort, as shown in FIG. 24g. The septum notch 264 would beprovided in region 265, as shown in FIG. 24c. FIGS. 24a and 24 b showfront and rear views of the cushion 40. In an alternative embodiment, aseptum notch may also be provided on the underlying frame.

[0178] The cushion 40 preferably has a generally trapezoidal shape inthis embodiment. However, the cushion 40 may have a non-trapezoidalshape such as a triangular shape. The cushion 40 includes a pair ofcheek regions 41 to provide a seal in the crease between the cheeks andthe sides of the nose, a lip region 42 provided to provide a seal belowthe nose and above the upper lip of the patient, and a nasal bridgeregion 43. The nasal bridge region 43 spans across the lower portion ofthe bridge and sloping sides of the bridge that intersect with the nasalcrease formed between the cheeks and the sides of the nose. Thetransition between the lip region 42 and each cheek region 41 is wherethe cushion 40 begins to turn around the bottom of the nose towards theside of the nose. The transition between the nasal bridge region 43 andeach cheek region 41 is where each cheek region 41 diverges upwardlytowards the bridge of the nose. In other words, the nasal bridge region43 starts where the cheek region begins to angle upwardly. See FIG. 24d.

[0179] The nasal bridge region 43 is designed to contact the patient'snose, for example, as shown in FIG. 1, where it can be seen that thelower portion of the bridge is selected for contact. Note that FIG. 1shows the cushion 40 spaced away from the frame. However, pictures inAppendix C of incorporated U.S. Provisional Application of Moore et al.,Serial No. 60/402,509, show the nasal mask assembly attached to twomodel noses (A & B), described further below. More specifically, thenose includes relatively bony sections at the upper portion of thebridge, and flexible cartilage at the tip of the nose. Reference may behad to Gray's Anatomy, Thirty-Eighth Edition (1995), FIGS. 6.133A, B,6.135A and 11.3A, B, incorporated herein by reference for drawingsshowing these regions. It is desirable to avoid localized pressurepoints along the bony region of the nose, to increase comfort to thepatient. Conversely, it is desirable to avoid mask contact with only thecartilage portion of the nose, because its flexibility may allow toomuch unwanted movement of the cushion in use, may occlude the nasalpassages of the patient, and may not provide a stable fit. In addition,positioning on the tip of the nose may increase the distance between thecenter of gravity of the mask assembly of the face of the patient—anundesirable consequence.

[0180] Accordingly, the optimal region of sealing engagement between thecushion and the bridge is somewhere between the uppermost bony regionand the lower cartilage region of the nose. Optimally, the region ofcontact is just above the cartilage on the bone. Generally, the cushioncan sit on the bone along the center of the nose, but it needs to avoidareas of cartilage on the sides of the nose. The nasal length and otherappropriate dimensions can be measured from the base of the nose and thetransition, or it can be obtained from statistical information on humananatomy. Samples of typical dimensions which are considered include oneor more of those found in FIGS. 30 and 31. However, the cushion may notcontact the patient in the lower nasal bridge region (positionedgenerally where the bony region of the nasal bridge transitions to aportion of the nose containing more cartilage) in all cases due todifferences in the facial contour for each individual patient.

[0181] The cushion 40 is designed to accommodate most of the patientpopulation (e.g., 80% of the patient population) in one or more sizes,preferably one to three sizes. The distance between the base of the noseand the top of the bridge is longer than the distance between the baseof the nose and the transition between bone and cartilage. The cushion40 can be made compact and/or lightweight since it need not accommodatethe entire length of the nose. This frees designers to optimize orimprove other areas of the cushion 40 and increases the patient's fieldof view while wearing the mask. Certain facial dimensions have beenidentified for optimal mask design to maximize the portion of thepopulation that can be accommodated. In one embodiment, a series ofcolor coded cushions is used. The cushion may be color coded for type orsize, for example.

[0182]FIGS. 24a-g show additional views of the cushion 40. As shown inFIG. 24e, the cushion 40 includes a frame 200 and a membrane 205attached to the frame. The frame 200 and membrane 205 are formed, forexample, in a one-shot injection molding process as is known in the art,using, e.g., silicone such as SILASTIC™ with 40 durometer hardness. Ofcourse, the frame 20 and the membrane 205 can be formed from twodifferent pieces that are connected together and/or to the frame 20. Theframe 200 has an edge 210, which may be attached to the channel 26 ofthe frame 20, as described in relation to FIGS. 27a-29 d. The edge 210of the frame 200 may be attached to the frame 200 with clips, straps,friction or interference, direct molding to the frame, adhesives and/ora tongue and groove arrangement, as is known in the art. The edge 210and a central portion or sidewall 215 above the edge 210 has a thicknesswhich is able to withstand buckling forces which can be applied when thecushion 40 is placed in engagement with the channel 26 of the frame. Inone form the central portion 215 has a thickness of 2-10 mm, preferably5 mm. The central portion 215 extends from the edge 210 to a transitionline 220 where the thin membrane 205 joins with the underlying frame200, between the frame 200 and the membrane 205. In the preferredembodiment, the height of the central portion 215 of the frame 200 ismost in the cheek regions 41 and less in the lip and nasal bridgeregions 42, 43.

[0183] Beyond the transition line 220, the frame 200 includes a rim 225.In a preferred form, the rim 225 has a curved shape that curves inwardlyinto the nasal cavity of the cushion 40. In an alternative form, the rimmay be provided by a solid piece having a generally round cross-section.The membrane 205 forms a seal forming portion 270 (FIG. 24e) whichcontacts the patient in the lower nasal bridge region, cheek and lipregions 41-43. The rim 225 has a thickness that is preferably less thanthe central portion 215 of the frame 200, but preferably greater thanthe membrane 205. For example, the membrane 205 has a thickness in therange of between about 0.1-2.0 mm, and preferably 0.35 mm, while the rim225 has a thickness of between about 0.5 and 2.0 mm, and preferably 1.35mm. While it is preferable that the membrane 205 be thinner than the rim225, they could have the same thicknesses. The membrane 205 completelycovers and surrounds the rim 225 of the frame 200, as shown in FIG. 25.The inside surface of the membrane 205 is spaced from the outsidesurface of the rim 225 so as to form a compliant seal with the patient.By compliant seal, it is meant that the membrane 205 can accommodatesmall variations in the shape of a patient's facial/nasal featureswithout undue force, and can account for small movement of the maskrelative to the patient during use, while maintaining an effective seal.The membrane 205 is preferably spaced away from the rim 225 at least inthe nasal bridge region 43, especially at a region 43 a near the apex ofthe nasal bridge region 43 (FIG. 24c). This is because that area of thepatient is most sensitive to localized contact pressure. Stateddifferently, the membrane 205 is preferably the only portion of thecushion 40 that contacts the patient to apply a sealing force to thepatient in the lower portion of the nasal bridge region 43. The membrane205 can better evenly distribute the force across the entire bridge ofthe nose, applying a lighter pressure, thereby improving comfort. Ofcourse, the sealing force applied to the transition between the bonyregion and the cartilage region of the nose is not so great as topartially or wholly close the nasal vents.

[0184] The rim 225 in the nasal bridge region, especially at the apexthereof, is spaced a sufficient distance away from the membrane 205 toavoid localized pressure points or regions on the lower bridge region ofthe nose. Moreover, the rim 225 should be inwardly curved to evenlydistribute forces which may cause the membrane 205 to contact the rim225. Such forces may be the result of over tightening the headgear 80 orinstability due to patient movement. The cushion 40 is designed to avoidcontact between the rim 25 and the membrane 205 in the lower nasalbridge region even if the headgear 80 is over-tightened. In that event,the rim 225 in the lower nasal bridge region (at least at the apex 43 a)can be eliminated to save material and weight, so long as the structuralintegrity of the cushion 40 is not compromised. Moreover, the rim 225need not be curved along the entire perimeter thereof, especially thoseportions that are designed not to contact the membrane 205 in use.

[0185] Spacing between the membrane 205 and the rim 225 in the cheek andlip regions 41, 42 is not necessary, but will add comfort and enable thecushion 40 to fit a wider range of patients due to the compliantmembrane 205.

[0186] A cushion in accordance with the invention provides improvedstability over prior art cushions. The footprint, or contact area hasbeen maximized, particularly along the sides of the nose. The sidecontact regions of the cushion have been maximized. This provides twofurther advantages. First, since the side walls of a cushion inaccordance with the invention are longer than some prior art cushions,it is possible to design a mask which seals above the nasal vents butbelow the upper portion of the nasal bridge. Second, by distributing thecontact pressure over a larger footprint, or contact area, stability ofthe mask assembly is improved. As such, the cushion 40 is much lesslikely to rotate in the vertical plane, as compared to prior art maskswhich tend to rotate about an axis substantially over the lip region.

[0187]FIGS. 25d-25 i show cross sections of the cushion 40. As shown inFIG. 25d, the distance between the rim and the membrane in the nasalbridge region 43 is in the range of about 5-14 mm, preferably 9 mm. Asshown in FIG. 25e, the distance between the rim and the membrane is inthe range of about 7-16 mm, preferably 11 mm. As shown in FIGS. 25f, 25g, 25 h, and FIGS. 25d and 25 i in the lip region, the distance is inthe range of about 1-6 mm, preferably 4 mm.

[0188]FIGS. 25d-25 i also show various other dimensions in one preferredembodiment, such as the radii of curvature, the angles at which themembrane extends, etc. For example, at the apex of the nasal bridgeregion, in FIG. 25d, the radius of curvature of the membrane is in therange of about 514 mm, preferably 9 mm, with an angle of about 70-90degrees, preferably 80 degrees. As shown in FIG. 25e, the radius ofcurvature is within the range of about 4-10 mm, preferably 7 mm, with anangle of about 50-70 degrees, preferably 60 degrees. Generally, thespacing in the nasal bridge region 43 should be more than the spacing inthe cheek and lip regions 41, 42. Of course, a cushion with a combinedmembrane and rim could be provided as well, e.g., a one layer structure.Conversely, the support function of the rim 225 could be accomplishedusing two or more support rims to support the membrane 205, or two ormore membranes could be provided over a single rim. In anotheralternative, the support function of the rim and the sealing function ofthe membrane can be split into two different members, which may be madeof different materials.

[0189]FIG. 24e shows that the membrane 205 includes a preformed,contoured notch 255 in the nasal bridge region 43 to match generally thetypical contours of the lower portion of the bridge region of thepatient. The frame 200 includes a notch 260 which is co-located inrelation to the notch 255. The shape of the notch 255 is generallyU-shaped, while the shape of the notch 260 is generally wider than thenotch 255, and the notch 260 is generally U-shaped. As shown in FIG.24f, the notch 255 has a depth d₁ in the range of 12-27 mm.

[0190] As seen in FIGS. 24a-c, an inner edge 230 of the membrane 205defines an aperture 235 of the membrane 205. In this preferred form, theshape of the aperture 235 is generally trapezoidal and has a base widthw of about 31-45 mm, sides with a length s of 20-22 mm, and a topportion t, generally parallel to the base portion with a length of about5-10 mm. See FIG. 24c. The included angle α is in the range of 45°-55°,and preferably 50°. The height h between the base portion and the topportion of the membrane 205 is in the range of 19-22 mm. Further, theoverall height h_(o) of the cushion 40 is in the range of 45-55 mm,preferably 50-51 mm and the overall width w_(o) of the cushion 40 is inthe range of 65-75 mm, preferably 69-71 mm. Also, as shown in FIG. 24f,the dimension d₂ of the cushion is in the range of 29-31 mm and thedimension d₃ of the cushion is in the range of 41-43 mm. In oneembodiment of a cushion 40 that has a “standard size”, the membrane 205of the cushion 40 has a width w in the range of 31-34 mm, preferably 33mm, a height h in the range of 19-28 mm, preferably 22 mm, and the notch255 has a depth d₁ in the range of 19-23 mm, preferably 21.5 mm. Inanother embodiment of a cushion 40 that has a “deep” size, the membrane205 of the cushion 40 has a width w in the range of 31-34 mm, preferably33 mm, a height h in the range of 19-28 mm, preferably 22 mm, and thenotch 255 has a depth d₁ in the range of 22-27 mm, preferably 24 mm. Inyet another embodiment of a cushion 40 that is wider and/or shallower indepth (“wide/shallow”), the membrane 205 of the cushion 40 has a width win the range of 35-45 mm, preferably 41 mm, a height h in the range of19-28 mm, preferably 22 mm, and the notch 255 has a depth d₁ in therange of 12-20 mm, preferably 16 mm. It is to be understood that thesedimensions refer to a particular embodiment of the invention, and adifferently sized mask (for example, a “small” size versus a “large”size) while having the same shape would have different dimensions andnevertheless be within the scope of the invention. Further, while the“standard” size cushion, “deep” size cushion, and “wide/shallow” sizecushion may be provided individually, these cushions may be providedtogether as a set of cushions. This set of three cushions provides agood fit in a wide range of patients without having an excessiveinventory.

[0191] The sides s of the membrane 205 adjacent the aperture 235 includea curved portion 250 (FIG. 24c) between the nasal bridge 43 and lipregions 41. The curved portion 250 appears as a bulged portion curvinginwardly toward the aperture 235. In FIG. 24f, the curved portion 250appears outwardly bulged in relation to the adjacent surfaces. FIG. 24ealso shows the depth of the notch 255 provided in the membrane 205 inthe nasal bridge region, as seen from the top view. FIG. 24d providesyet another view of the curved portion 250, and the shape of themembrane 205 in relation to the underlying shape of the rim 225. Thecurved portion 250 helps provide a good seal along the sides of the nosein the crevice where the cheek meets the nose. For example, as seen inFIG. 24c, the portion 250 is spaced away from the edge of the rim 225 sothat more allowance for sealing in the crease and along the sides of thenose is provided. The edge 240 of the rim 225 and the edge 230 of themembrane 205 in the cheek region 41 begin diverge away from one anotherat an angle, as seen in FIG. 24c. The spacing between the edges 230, 240of the membrane 205 and the rim 225 are smallest in the lip region 42,and gradually increases in the cheek regions 41, and is most in thecurved portion 250 and nasal bridge region 43, as shown in FIGS. 25e-25i.

[0192] The inner edge 240 of the rim 225 which defines an aperture 245is shown in FIG. 24b. The base width W of the aperture 245 is in therange of 38-45 mm. The length of each side S is in the range of 20-23mm. The length of the top portion T is in the range of 15-20 mm. Theheight H between the base portion and the top portion of the is in therange of 32-36 mm. These dimensions, and all other dimensions providedherein, are preferred dimensions and could be changed depending on theparticular application. While the shape of the aperture can also becharacterized as generally trapezoidal, the trapezoid is not in the sameproportions to the trapezoidal shape of the aperture 235 of the membrane205. The aperture 235 is smaller than the aperture 245.

[0193] Further, the apertures 235 and 245 may have a triangular shape orother non-trapezoidal shape. Further, the overall shape of the cushionmay be triangular or non-trapezoidal. The shapes of the apertures 235and 245 and cushion may be similar to one another or may be different,e.g., the aperture 235 has a trapezoidal shape and the aperture 245 hasa triangular shape.

[0194] The width of the membrane 205 as measured from the transitionline 220 to the edge of the membrane 205 is greatest in the curvedportion 250 and nasal bridge region 43, less in the cheek regions 41,and the least in the lip region 42. The membrane 205 generally extendsupwardly away from the transition line 220 in the nasal bridge, cheekand lip regions 41-43. In the nasal bridge region 43, the membrane 205curves inwardly along a generally constant radius to terminate at theedge 230. In the cheek regions 41, the membrane 205 curves around therim 225 and then inwardly away from the rim 225 at an angle generallytoward the opposite bottom position of the frame 200. In the lip region41, the rim 225 and the membrane have substantially the same shape. SeeFIGS. 25d-25 i.

[0195] Mask Frame and Cushion Connection System

[0196] The mask of the present invention may be fabricated in a mannerwhere the mask frame and mask cushion are permanently attached to eachother. For example, the mask frame and cushion may be formed from thesame material in one piece where the elbow is attached as a separatepiece. Alternatively, the mask frame and cushion may be formed as twopieces of the same or different material where the cushion and maskshell are attached in a permanent manner. The permanent attachment maybe achieved through co-molding, adhesives, the use of clips or othermechanical means.

[0197] Alternatively, the mask frame and cushion may be attached by wayof a method that allows for it to be detached and then re-attachedrepeatedly through the useful life of the mask, as will be describedbelow. This allows for disassembly for effective cleaning andmaintenance or even allows replacement if a part is worn out.

[0198] The mask shell and cushion connection system of the presentinvention allows for the manufacture of a combination mask frame andcushion that allows for the independent determination of forces forengagement of the cushion and disengagement of the cushion from theframe. Because of this ability, it is possible to fabricate a maskconnection system where the engagement force is equal to thedisengagement force, or where the engagement force is less than thedisengagement force, or where the engagement force is greater than thedisengagement force.

[0199] The connection system may be designed to achieve a disengagementforce that is less than or greater than the force asserted upon the masksystem at maximum treatment pressure.

[0200] Preferably the disengagement force (i.e. the force that willdetach the cushion from the mask frame) will be greater than the forcethat would be asserted against the mask shell and cushion combinationwhen the maximum treatment pressure is achieved in the mask chamber. Bysetting this lower limit for the disengagement force by reference tothat force asserted against the frame and cushion combination, thelikelihood of a mask disengaging during the application of treatmentpressure is reduced.

[0201] While the minimum disengagement force is preferably determined byreference to the force asserted by treatment pressure, the maximumdisengagement force ought to be no greater than the force that iscapable of being comfortably exerted by a user when manually disengagingthe mask to prevent inadvertent release and annoyance to the user.Preferably, the displacement force will be no greater than the forcethat may be comfortably exerted by a user.

[0202] The engagement force for the cushion (that is the force requiredto correctly connect the cushion to the mask shell) may be predeterminedand achieved by adoption of the sealing and retaining mechanisms of thepresent invention.

[0203] Preferably the engagement force will be no greater than the forcethat may be comfortably exerted by the user. As the present inventionhas application in a mass-produced product range, preferably the maximumengagement force will be no greater than the force that may be exertedby the target user population. In a clinical setting that targetpopulation may be the clinical staff who will be fitting and applyingthe mask to patients. In a non-clinical setting that target populationmay be the population of end users. Preferably the target engagementforce would be determined by considering the preferred engagement forcethat may be exerted by the target population when manipulating the maskshell and cushion in a conventional manner. Of course, these principlesalso apply to the disengagement force as well.

[0204] In one embodiment of the nasal mask assembly 10, an improvedmechanism is used for engaging, i.e., retaining and sealing, the cushion40 to the frame 20. See FIGS. 27a-29 d. With the retaining and sealingmechanism, the cushion 40 can be fitted to the mask frame 20 in onemovement that retains the cushion 40 and forms a secure seal with theframe 20. Outer wall 30 of channel 26 on frame 20 is provided with aplurality of undercuts 33 spaced around the outer wall 30. The undercuts33 can pass partially or completely through the outer wall 30. A slighttaper can be provided to the interior surfaces of inner wall 28 andouter wall 30 to ease assembly of the cushion 40 to the frame 20. Thecushion 40 includes a side wall 215. As shown in FIG. 25d, the side wall215 has a width b of about 5 mm. The side wall 215 includes a pluralityof retention lips 44, spaced around the side wall 215 to align with theundercuts 33. Each retention lip 44 includes a leading edge 45, taperedto ease insertion of the cushion 40 into the channel 26, and a retentionsurface 431, shaped to catch the undercut 33 and prevent separation ofthe cushion 40 from the frame 20 until a predetermined separation forceis applied between the cushion 40 and the frame 20. Preferably thepredetermined separation force is designed to be greater than the forceto insert the cushion 40 into the channel 26. Distally positioned on theside wall 215 are upper and lower sealing lips 46 and 47 extendingoutward from the side wall 215 and running around a periphery of theside wall 42. Opposite the sealing lips 46 and 47 are upper and lowersealing lips 49 and 48 extending inward from the side wall 215 andrunning around an inner periphery of the side wall 215. Opposite theretention lips 44, the inner surface of the side wall 215 has a relievedportion 50 thus creating a space between the wall of the cushion and thechannel allowing the wall of the cushion 40 to distort into the relievedportion 50, as shown in FIGS. 27b and 27 e, making insertion of thecushion 40 easier. The relieved portion 50 can be positioned justopposite each retention lip 44 or the relieved portion 50 can extend allthe way around an inner periphery of the side wall 215.

[0205] Assembly of the cushion 40 to the frame 20 according to oneembodiment of the invention will now be described. The cushion 40 isfirst generally aligned with the channel 26. See FIG. 27a. The innerwall 28 is slightly higher than the outer wall 30 to assist in aligningthe cushion 40 with respect to the channel 26 before the cushion 40enters the channel 26. The cushion 40 is then moved into the channel 26.See FIG. 27b. The leading edge 45 of each retention lip 44 will engage atop portion of the outer wall 30 and begin to deform. The relievedportion 50 of the side wall 215 allows this deformation to happenwithout greatly increasing the force necessary to insert the cushion 40into the frame 20. The sealing lips 46-49 have contacted the respectivesurfaces of the inner and outer walls 28 and 30 of channel 26. Thecushion 40 is further inserted into the channel 26 until it bottomsagainst the channel floor 32. See FIG. 27c. The sealing lips 46-49 arein full contact with the inner and outer walls 28 and 30. Each retentionlip 44 has entered the respective undercut 33 but there is stilldeformation of the side wall 215, accommodated by the relieved portion50. The cushion 40 is then slightly withdrawn as compression of theelastomer (Silastic™) relaxes from the channel 26, seating the retentionsurface 431 of each retention lip 44 against the respective undercut 33,with the sealing lips 46-49 in continuous sealing position around theinner and outer walls 28 and 30. See FIG. 27d. This withdrawal andseating provides a tactile signal to the user that the cushion 40 isproperly seated in the channel 26. If the undercuts 33 are made visibleto the user in this position, a visual indicator of seating is alsoprovided. Deformation of the side wall 215 has generally been removed atthis point and the relieved portion 50 returned to its relaxedconfiguration. Further withdrawal of the cushion 40 from the channel 26,to disassemble the cushion 40 from the frame 20 will deform theretention lip 44 downward. See FIG. 27e. This deformation of the sidewall 215 will again be accommodated by the relieved portion 50. Theshape of retention lip 44 results in the preferred more secure removalforce compared to assembly force by the user.

[0206] Furthermore, where the cushion sealing lips or retention lip orboth are made of a material that expands over time such as with somechemical cleaning exposure (i.e. increases in size in at least onedimension) such a material being silicone, the extra size or volumeresulting from spread of material may be accommodated within the channel26, say by the sealing lips or retention lip flexing. This aspect of theinvention has advantages over the prior art in that the spread ofcushion material ought not compromise the seal of the mask shell andcushion, thereby prolonging the useful life of the component made of theexpandable material.

[0207] The prior art typically requires the cushion material to achievea snug fit with the frame so as to prevent leakage of gas from the maskchamber via one or more paths between the frame and cushion. In additionsome masks utilized an interior or exterior cushion clip to sandwich thecushion between the clip and the frame. Such cushion clips are found inRespironics' ComfortSelect mask, and in ResMed's Ultra Mirage™ mask,which is described in U.S. Pat. No. 6,412,487, incorporated herein byreference.

[0208] With the prior art, should the cushion be made of a material thatspreads with time, there is a tendency for the material to increase inat least one plane to the extent that it becomes difficult to fit ordisengage from the mask frame channel, or to otherwise make use of acushion clip. Also, the seal to prevent gas escaping from the maskchamber is compromised due to gaps appearing between the cushion sealportion and the mask frame channel. The prior art limitations have beendescribed with reference to a mask which has the sealing channel locatedin the frame and the sealing edge located on the cushion. However,similar limitations will apply where the location of these features arereversed, that is to say where the sealing channel is located on thecushion and the sealing edge is located on the mask shell as well aswhere the interface between the cushion and mask shell surface are inthe form of flat surfaces.

[0209] As treatment pressure within the mask chamber is not beingachieved during mask assembly, the selection of engagement pressure isnot necessarily determined by reference to the force exerted duringtreatment. Rather, it is possible to fabricate the connection system ofthe present invention so as to achieve an engagement force that is lessthan the disengagement force—such a configuration, where the engagementforce is less than the disengagement force is consistent with data thatany given human population is typically capable of exerting a pullingforce (i.e. where one or two hands move away from a starting point whilegripping an object) than they are capable of exerting a pushing force(i.e. where one or two hands move towards a fixed point while grippingan object).

[0210] The embodiment described above can maintain the relationship of adisengagement force being greater than an engagement forcenotwithstanding that a dimension of a component may change overtime—such as is the case where the cushion is made of a material thatexpands over time such as is the case with silicone.

[0211] The embodiments of the present invention also overcome the priorart limitation of loss of friction fit where at least one component suchas the cushion is made of a material that tends to lose its frictionalquality over time, such as with silicone which material tends to become‘greasy’ due to chemical change and its own absorption of environmentalpollutants, such as the patient's skin oil. Accordingly, the presentinvention addresses the prior art problem of a loss of engagement effectbetween the frame and cushion over time notwithstanding the loss of thefriction between them.

[0212] While the present invention teaches away from the need for strap,clip or other additional retaining devices, such devices may be includedin the fabrication so as to add further security of engagement betweenframe and cushion or to otherwise reduce the design tolerances requiredto achieve a disengagement force that is consistent with the upper limitconsidered appropriate for the target population while maintainingengagement during the maximum treatment pressure.

[0213] The cushion 40 includes at least one sealing lip which functionsto prevent escape of gas from the mask chamber via the interface betweenframe and cushion. Preferably there are provided at least two seal lipseach having relatively small contact points with the frame channel 26 asshall be described so as to minimize the friction occurring duringassembly and disassembly of the cushion with the frame withoutcompromising the seal.

[0214] If one seal lip were used, then its configuration to achieveadequate sealing may require it to assert greater friction once inposition than would be the case where there were adopted two or moreseal lips of the same material.

[0215] By control of this source of friction, it is possible toinfluence the engagement and disengagement forces, i.e., the forcesrequired to engage and disengage the cushion and frame. The preferredaim being to have those forces remain with defined limits for theexpected useful life of the cushion.

[0216] The relieved portion 50 of the side wall also accommodatesdeformation of the side wall 215 upon assembly and disassembly of thecushion 40 and frame 20, thereby reducing the force necessary forassembly/disassembly. This is especially important where the cushion 40is made from a pliable but generally slightly compressible material,such as silicone. Alternatively, the inner wall 28 can be provided withan undercut 29 opposite each undercut 33 to accommodate deformation ofthe side wall 215. See FIG. 28. The undercut 29 (and/or relieved portion50) can be sized and configured as desired to best accommodate theexpected side wall deformation. Different combinations of the sealinglips 46-49 can alternatively be used. See, for example, FIG. 29a(sealing lips 47 and 48), FIG. 29b (sealing lips 46 and 49), FIG. 29c(sealing lips 48 and 49) and FIG. 29d (sealing lips 46 and 47). Otherconfigurations of sealing lips and retention lips can also be used. Thisconfiguration separates the sealing function of cushion to frame fromthe functions of cushion and frame engagement and retention, so thateach may be independently controlled and optimised in deviceconfiguration and fabrication.

[0217]FIGS. 32a-1-32 c-2 show sequential engagement between the frame 20and the cushion, according to another embodiment of the presentinvention. In this embodiment, the side wall 215 has been changed, aswell as the channel 26 which receives the side wall 215. FIGS. 32a-1-32a-2 show the frame and cushion before engagement, FIGS. 32b-1-32 b-2show the frame and cushion during engagement and FIGS. 32c-1-32 c-2 showthe frame and cushion in full engagement.

[0218] In this embodiment, the side wall 215 preferably includes anintegral lug 215 a at a distal end of the side wall 215. The side wall215 includes an undercut 215 b which allows the lug 215 a to flex towardthe side wall 215. During insertion (FIGS. 32b-1-32 b-2), the lug 215 aflexes into the undercut 215 b until it is pushed beyond a protrusion 26a in the channel 26. After passing the protrusion 26 a, the lug 215 aflexes into a space of the channel 26 below the protrusion 26 a.Therefore, the tip of the lug is positioned to be resiliently locked inplace with the cushion 40 fully and securely connected to the frame 20.In the connected condition, the side wall 215 provides a secure sealwith the frame 20 against escape of pressurized gas from the nasalcavity. Engagement between the tip of the lug 215 a and the protrusion26 a provides a retaining force to maintain the cushion in engagementwith the frame. To disengage, the patient pulls the side wall 215 out ofthe channel 26 with a force sufficient to cause the lug 215 a to deformand overcome the protrusion 26 a. Both engagement and disengagementrequire a force that is enough to overcome the frictional contactbetween the walls of the channel 26 and side wall 215. As the angle ofprotrusion 26 a is substantially away from the insertion direction, itacts in much the same way as a “barb” allowing the preferred lowerinsertion force compared to disassembly force of the cushion to maskframe.

[0219] In the illustrated embodiment, the lug 215 a at the distal end ofthe side wall 215 extends generally inwardly towards the breathingcavity of the cushion. However, as shown in FIG. 32e, the lug 215 a mayextend generally outwardly from the breathing cavity of the cushion 40and engage a protrusion 26 a provided on the outer wall 30 of the frame20.

[0220] FIGS. 40-41 illustrate another embodiment of the frame 20 that isstructured to facilitate the engagement between the frame 20 and thecushion 40. Specifically, the main body 20 a of the frame includesalignment symbols A₁, e.g., diamonds, lines, colors, arrows, etc., onthe outer surface of the outer wall 30 thereof. FIG. 40 illustrates asingle alignment symbol A₁ provided on an upper portion of the outerwall 30 and FIG. 41 illustrates a pair of alignment symbols A₁ providedon a lower portion of the outer wall 30.

[0221] The cushion 40 includes alignment symbols A₂, e.g., diamonds,lines, colors, arrows, etc., on the outer surface thereof that arepositioned to align with the alignment symbols A₁ provided on the frame20 when the cushion 40 and frame 20 are engaged with one another. FIGS.38B, 39B, and 42 illustrate a single alignment symbol A₂ provided on theouter surface of the cushion 40 in the nasal bridge region and FIG. 43illustrates a pair of alignment symbols A₂ provided on the outer surfaceof the cushion 40 in the lip region. When the cushion 40 and frame 20are engaged with one another, the alignment symbol A₁ on the upperportion of the frame 20 aligns with the alignment symbol A₂ in the nasalbridge region of the cushion 40. Similarly, the pair of alignmentsymbols A₁ provided on the lower portion of the frame 20 align with thepair of alignment symbols A₂ in the lip region of the cushion 40. Thealignment of the alignment symbols A₁, A₂ on the frame 20 and cushion40, respectively, ensures that the frame 20 and cushion 40 are correctlyaligned and oriented with respect to one another. That is, the patientcan correctly engage the frame 20 and cushion 40 by ensuring that thealignment symbols A₁, A₂ on the frame 20 and cushion 40 are correctlyaligned with one another.

[0222] The alignment symbols A₁, A₂ may have any suitable configuration,e.g., diamonds, lines, colors, arrows, etc. Also, any correspondingnumber of alignment symbols A₁, A₂ may be provided on the frame 20 andcushion 40. In the illustrated embodiment, the upper portion of theframe 20 and the nasal bridge region of the cushion 40 have a differentnumber of alignment symbols A₁, A₂ than the lower portion of the frame20 and the lip region of the cushion 20. However, the upper and lowerportions of the frame 20 and the respective nasal bridge and lip regionsof the cushion 40 may have the same number of alignment symbols A₁, A₂so long as the alignment symbols A₁, A₂ are positioned to facilitatecorrectly engaging the frame 20 and the cushion 40 in the correctorientation. Further, the alignment symbols A₁, A₂ may be positioned atany suitable location along the outer surfaces of the frame 20 and thecushion 40 to facilitate the engagement between the frame 20 and thecushion 40.

[0223] As shown in FIG. 40, the frame 20 may include alignment symbolsA₁, e.g., diamonds, lines, colors, arrows, etc., on the side framemembers 20 b which are structured to facilitate the engagement betweenthe frame 20 and the headgear assembly 80. Specifically, the lockingclip 82 of the headgear assembly 80 may include alignment symbols, e.g.,diamonds, lines, colors, arrows, etc., on the outer surface thereof thatare positioned to align with the alignment symbols A₁ provided on theframe 20 when the locking clip 82 and frame 20 are engaged with oneanother.

[0224] Other Aspects

[0225] A nasal cushion was designed taking into account the shape andsize of the nose of the patient, along with the size and shape of thesurrounding facial features, such as the upper lip, the cheeks, etc. SeeFIGS. 30-31. While there is little statistical information regarding thesizes and shapes of those patients likely using or in need of some sortof NPPV treatment, Applicants have discovered that a select amount ofcriteria can be used to statistically model the cushion 40 to fit a vastmajority of the patient population (e.g., 80% of the patientpopulation). For example, the cushion 40 may be structured toaccommodate 60-90% of patient population, regardless of age, sex, orrace. However, the cushion 40 may be structured to accommodate up to 70%or up to 80% of patient population, for example. Using nasal width,nasal tip protrusion and nose height, Applicants have been able todesign the cushion such that a large proportion of the population likelyto be in need of nasal masks can be accommodated comfortably with thesame sized cushions/masks. One or two additional cushions/masks can bedesigned to accommodate other parts of the population. Age, race and sexof the patient can be factors in computer modeling the cushion.Moreover, by designing a cushion in which contact with the upper portionof the nasal bridge portion is avoided, Applicants have been able toeliminate one of the factors which limits the designs of cushions ingeneral.

[0226] As shown in FIGS. 30 and 31, the nasal width determines the widthof the opening in the cushion 40. Nasal tip protrusion describes minimumdepth of cushion and mask frame combined. This is measured from thebottom of the septum. A mask with too much depth may result in excessivedead space within the nasal cavity that increases undesirable CO₂re-breathing and movement of the center of gravity of the mask assemblyfurther away from the face decreasing stability. Nose height reflectsthe distance between both sets of width/depth dimensions.

[0227] In general, cushions are sized to fit one or more maximumdimensions. However, user testing is important in verifying clearance atthe nasal vent. If too large, the cushion may interfere with the eyearea. The cushion is designed to sit low on the nasal bridge; possibleinterference in this area is minimized. If the cushion is too small,e.g., if the cushion applies pressure along the soft part of the nosethat may collapse, the nasal vent may be partially or fully occluded,causing breathing restriction, as can occur with some prior art maskssuch as the Respironics Simplicity mask. Nose width, height and tipprotrusion can be arrived at by reference to anthropometric data tables.

[0228] In one embodiment of the mask system, the mask system is designedto include a frame and a plurality of cushions that are each connectablewith the frame. Each cushion would be configured to accommodate apercentage of the patient population such that the plurality ofcushions, preferably 1-3 cushions, would together accommodate up to95-100% of the patient population.

[0229] Thus, the plurality of cushions would each have a similar framecontacting side but a different face contacting side. Each cushion wouldhave at least one parameter on the face contacting side that isdifferent from the remaining plurality of cushions. In one embodiment,each cushion may differ in the nasal bridge region. For example, thecushion 40 a shown in FIGS. 38A-38D has a deeper contoured notch 255 ain the nasal bridge region than the contoured notch 255 b in the nasalbridge region of the cushion 40 b shown in FIGS. 39A-39D. Specifically,the contoured notch 255 a has a depth d in the range of 22-27 mm,preferably 24 mm and the contoured notch 255 b has a depth d in therange of 1923 mm, preferably 21.5 mm. As illustrated, the notch 255 ahas a smaller radius of curvature than the radius of curvature of notch255 b. In another embodiment, each cushion may differ in the width ofthe aperture of the membrane. The plurality of cushions may be colorcoded to help distinguish the different cushions from one another.

[0230] Appendix A of incorporated U.S. Provisional Application of Mooreet al., Serial No. 60/402,509, includes various pictures of the masksystem according to one preferred embodiment of the present invention.Appendix A also includes various pictures of the mask system accordingto other embodiments of the present invention. For example, anembodiment of the frame is provided that illustrates a frame havingoxygen or pressure ports. See, e.g., FIG. 41. Further details of oxygenor pressure ports in a frame are included in U.S. Patent applicationSer. No. 09/504,234, the entirety of which is hereby incorporated byreference. Appendix A also includes instructional information for themask system. Appendix B of incorporated U.S. Provisional Application ofMoore et al., Serial No. 60/402,509, includes pictures of two prior artmasks discussed in the present invention. Appendix C of incorporatedU.S. Provisional Application of Moore et al., Serial No. 60/402,509,includes pictures of two testing models (A+B) with widely varying noseand facial features, and the mask assembly of the present invention aswell as one prior art mask connected to each model. Appendix C alsoincludes a series of pictures comparing one embodiment of the presentinvention to a prior art cushion used for the MIRAGE® mask. See, e.g.,U.S. Pat. No. 6,112,746 to Kwok et al., incorporated herein byreference. Generally speaking, the mask assembly of the presentinvention generally conformed to both nose models even though the sizesand shapes were vastly different. The mask cushion 40 also was able tosuccessfully accommodate the deformity on model B. The mask assembly ofthe prior art tended not to fit the shape of the nose models, especiallythe shape of the smaller nose model where significant gaps are seen. Oneprior art model (see U.S. Pat. No. 5,724,965) was relatively unstableand tended to rock on the cheeks of the models, especially the smallernose model.

[0231] It is intended that the components, elements and features of thevarious above-described embodiments can be used together in any desiredcombination or permutation to create new mask embodiments. For example,while the invention has been described in relation to a nasal mask, theteachings are also applicable to oro-nasal and full-face masks as well.

What is claimed is:
 1. A respiratory mask assembly for deliveringbreathable gas to a patient, comprising: a frame having a front surfaceand a rear surface adapted in use to face the patient; and a cushionhaving a side wall removably attachable to the frame, the cushion havinga rim extending away from the side wall, and a membrane provided tosubstantially surround the rim, wherein an inner edge of the membranedefines an aperture, the aperture having a generally trapezoidal shape.2. A respiratory mask assembly according to claim 1, wherein themembrane is adapted to form a seal on the patient's nasal bridge regionpositioned substantially along a transition between the bony region andthe cartilage region of the patient's nose.
 3. A respiratory maskassembly according to claim 2, wherein the membrane is adapted to form aseal on the patient's lip region positioned below the patient's nose andabove the upper lip of the patient.
 4. A respiratory mask assemblyaccording to claim 3, wherein the membrane includes a notch toaccommodate a septum on the patient's lip region.
 5. A respiratory maskassembly according to claim 1, wherein, in at least a portion of a nasalbridge region of the patient positioned substantially along a transitionbetween the bony region and the cartilage region of the patient's nose,the rim and the membrane are spaced away from one another to define agap.
 6. A respiratory mask assembly according to claim 1, wherein themembrane includes a contoured portion that extends upwardly from theside wall and curves inwardly along a generally constant radius toterminate at an inner edge of the membrane, the contoured portionincluding a gap between the rim and the membrane, the gap being maximumin the contoured portion, and wherein the contoured portion is providedin a transition between cheek and nasal bridge regions of the cushion.7. A respiratory mask assembly according to claim 1, wherein themembrane includes a contoured notch in a nasal bridge region of thecushion positioned substantially along a transition between the bonyregion and the cartilage region of the patient's nose to conform to thecontours of the patient's nasal bridge region.
 8. A respiratory maskassembly according to claim 7, wherein the contoured notch has a depthin the range of 12-27 mm.
 9. A respiratory mask assembly according toclaim 1, wherein the aperture has a base portion with a length in therange of 31-45 mm, sides with a length in the range of 20-22 mm, and atop portion parallel to the base portion with a length in the range of5-10 mm.
 10. A respiratory mask assembly according to claim 1, whereinan inner edge of the rim defines an aperture, the aperture of themembrane having a smaller dimension than a dimension of the aperture ofthe rim.
 11. A respiratory mask assembly according to claim 10, whereinthe aperture of the rim has a generally trapezoidal shape.
 12. Arespiratory mask assembly according to claim 11, wherein the aperture ofthe rim has a base portion with a length in the range of 38-45 mm, sideswith a length in the range of 20-23 mm, and a top portion parallel tothe base portion with a length in the range of 32-36 mm.
 13. A cushionfor a respiratory mask assembly that delivers breathable gas to apatient, the cushion comprising: a side wall structured to be removablyattached to a frame; a rim extending away from the side wall; and amembrane provided to substantially surround the rim, wherein an inneredge of the membrane defines an aperture, the aperture having agenerally trapezoidal shape.
 14. A cushion according to claim 13,wherein the membrane is adapted to form a seal on the patient's nasalbridge region positioned substantially along a transition between thebony region and the cartilage region of the patient's nose.
 15. Acushion according to claim 14, wherein the membrane is adapted to form aseal on the patient's lip region positioned below the patient's nose andabove the upper lip of the patient.
 16. A cushion according to claim 15,wherein the membrane includes a notch to accommodate a septum on thepatient's lip region.
 17. A cushion according to claim 13, wherein themembrane includes a contoured portion that extends upwardly from theside wall and curves inwardly along a generally constant radius toterminate at an inner edge of the membrane, the contoured portionincluding a gap between the rim and the membrane, the gap being maximumin the contoured portion, and wherein the contoured portion is providedin a transition between cheek and nasal bridge regions of the cushion.18. A cushion according to claim 13, wherein the membrane includes acontoured notch in a nasal bridge region of the cushion positionedsubstantially along a transition between the bony region and thecartilage region of the patient's nose to conform to the contours of thepatient's nasal bridge region.
 19. A cushion for a respiratory maskassembly that delivers breathable gas to a patient, the cushioncomprising: a side wall structured to be attached to a frame; and amembrane extending away from the side wall, wherein the membrane isstructured to engage a patient's face such that forces applied to thepatient's face are substantially evenly distributed around the entireperimeter of the cushion.
 20. A cushion according to claim 19, wherein acontact area between the membrane and the patient's face in a nasalbridge region positioned substantially along a transition between thebony region and the cartilage region of the patient's nose is greaterthan a contact area between the membrane and lip and cheek regions ofthe patient.